640631515631 has 2 divisors, whose sum is σ = 640631515632. Its totient is φ = 640631515630.

The previous prime is 640631515621. The next prime is 640631515633. The reversal of 640631515631 is 136515136046.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640631515631 is a prime.

It is a super-2 number, since 2×640631515631² (a number of 24 digits) contains 22 as substring.

Together with 640631515633, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640631515633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320315757815 + 320315757816.

It is an arithmetic number, because the mean of its divisors is an integer number (320315757816).

Almost surely, 2^640631515631 is an apocalyptic number.

640631515631 is a deficient number, since it is larger than the sum of its proper divisors (1).

640631515631 is an equidigital number, since it uses as much as digits as its factorization.

640631515631 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 194400, while the sum is 41.

The spelling of 640631515631 in words is "six hundred forty billion, six hundred thirty-one million, five hundred fifteen thousand, six hundred thirty-one".