The next big goal is to identify a prime number with 100 million digits

M74207281 has exactly 22,338,618 digits - five million more than the last

Prime numbers can only be divided by one and themselves

A number dubbed M74207281 has been confirmed as the largest prime number ever identified.

The prime - a number greater than one that is only divisible by one and itself – is more than 22 million digits long.

It begins with 200376, ends in 8646351 and has been described as a 'massive but entirely prime number'.

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A number dubbed M74207281 has been discovered that is the largest prime number ever to have been identified. It is shown above in short form. If the full number was printed out with each digit measuring one millimetre, it would be 13.9 miles (22.3km) long - or the equivalent to 1,487 London buses in a row

More simple prime numbers include, 2,3,5,7 and 13, but the search is on to find huge prime numbers, millions of digits long.

The latest number was discovered by Curtis Cooper at the University of Central Missouri, who is involved in the Great Internet Mersenne Prime Search (Gimps).

M74207281 has exactly 22,338,618 digits – five million more than the previous 'biggest prime number,' which Professor Cooper discovered in February 2013.

It was calculated by multiplying together 74,207,281 twos then subtracting one.

The latest number was discovered by Curtis Cooper at the University of Central Missouri, who is involved in the Great Internet Mersenne Prime Search (Gimps). The number was identified by a computer using Gimps software. Thousands of computers are working together to crunch numbers (stock image)

If it was printed out with each digit measuring one millimetre, it would be 13.9 miles (22.3km) long - or the equivalent to 1,487 London buses in a row.

WHAT ARE MERSENNE PRIMES? A prime number must be greater than one, and is only divisible by one and itself. The first prime numbers are 2, 3, 5, 7, 11 and so on. For example, the number 10 is not prime because it is divisible by 2 and 5. Mersenne primes are rarer. A Mersenne prime is one taking the form 2P-1, where P is a prime. The first Mersenne primes are 3, 7, 31, and 127 corresponding to primes of 2, 3, 5, and 7 respectively. There are only 49 known Mersenne primes. Mersenne primes have been central to number theory since they were first discussed by ancient Greek mathematician Euclid in about 350 BC. They are named after a French monk, Marin Mersenne who in his lifetime between 1588 and 1948, famously estimated which values of P would yield a prime. It took 300 years and several important discoveries in mathematics to settle his conjecture. Advertisement

The Gimps search is a group effort to spot new primes using computers.

The software automatically crunches numbers to see whether they are prime and Professor Cooper uses 800 computers to search for record-breakers.

One of his machines found M74207281 on 17 September, but a software bug meant an email notification of the discovery failed to be sent, meaning it went unnoticed for four months.

Professor Cooper described this as an 'embarrassment' in an interview on the 'Standup Maths' YouTube channel.

He told Matt Parker he got an email on the afternoon of 7 January telling him about the discovery.

To prove there were no errors in the prime discovery process, the prime was independently verified by two computer programs and different hardware.

'A human has to take notice of the machine's discovery, so even though it was 17 September 17 when the computer found it, it was 7 January when Aaron - a person doing database maintenance - found it. That's the date of discovery.'

Professor Cooper added: 'I still have the same excitement as when we were lucky enough to find the first one.'

He has found four record-breaking prime numbers. He received a $3,000 (£2,000) prize from Gimps for each discovery, New Scientist reported.

The new prime number is a member of a special class of extremely rare prime numbers known as Mersenne primes.

They take a certain form: 2 to the power of p, where p is also a prime, minus one.

The Gimps search is a group effort to spot new primes using computers. The software automatically crunches numbers to see whether they are prime and Professor Cooper uses 800 computers to search for record-breakers (stock image of a calculator is shown)

Mersenne primes were named for the French monk Marin Mersenne, who studied these numbers more than 350 years ago.

There are only 49 known Mersenne primes – the first are 3, 7, 31, and 127 - and the last 15 have been discovered thanks to Gimps.

While the prime numbers are infinite and of little practical use, they prove the incredible capability of computers and there's also money to be won.