640355923 has 2 divisors, whose sum is σ = 640355924. Its totient is φ = 640355922.

The previous prime is 640355899. The next prime is 640355939. The reversal of 640355923 is 329553046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640355923 - 2²⁵ = 606801491 is a prime.

It is not a weakly prime, because it can be changed into another prime (640355953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320177961 + 320177962.

It is an arithmetic number, because the mean of its divisors is an integer number (320177962).

Almost surely, 2^640355923 is an apocalyptic number.

640355923 is a deficient number, since it is larger than the sum of its proper divisors (1).

640355923 is an equidigital number, since it uses as much as digits as its factorization.

640355923 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 97200, while the sum is 37.

The square root of 640355923 is about 25305.2548495367. The cubic root of 640355923 is about 861.9335990863.

It can be divided in two parts, 640355 and 923, that added together give a triangular number (641278 = T₁₁₃₂).

The spelling of 640355923 in words is "six hundred forty million, three hundred fifty-five thousand, nine hundred twenty-three".