640991209597 has 2 divisors, whose sum is σ = 640991209598. Its totient is φ = 640991209596.

The previous prime is 640991209577. The next prime is 640991209601. The reversal of 640991209597 is 795902199046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 638610355161 + 2380854436 = 799131^2 + 48794^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640991209597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640991209517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320495604798 + 320495604799.

It is an arithmetic number, because the mean of its divisors is an integer number (320495604799).

Almost surely, 2^640991209597 is an apocalyptic number.

It is an amenable number.

640991209597 is a deficient number, since it is larger than the sum of its proper divisors (1).

640991209597 is an equidigital number, since it uses as much as digits as its factorization.

640991209597 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11022480, while the sum is 61.

The spelling of 640991209597 in words is "six hundred forty billion, nine hundred ninety-one million, two hundred nine thousand, five hundred ninety-seven".