640907591 has 2 divisors, whose sum is σ = 640907592. Its totient is φ = 640907590.

The previous prime is 640907573. The next prime is 640907621. The reversal of 640907591 is 195709046.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640907591 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640900591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320453795 + 320453796.

It is an arithmetic number, because the mean of its divisors is an integer number (320453796).

Almost surely, 2^640907591 is an apocalyptic number.

640907591 is a deficient number, since it is larger than the sum of its proper divisors (1).

640907591 is an equidigital number, since it uses as much as digits as its factorization.

640907591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 640907591 is about 25316.1527685389. The cubic root of 640907591 is about 862.1810472551.

The spelling of 640907591 in words is "six hundred forty million, nine hundred seven thousand, five hundred ninety-one".