640808565 has 16 divisors (see below), whose sum is σ = 1026478656. Its totient is φ = 341369600.

The previous prime is 640808551. The next prime is 640808603. The reversal of 640808565 is 565808046.

It is not a de Polignac number, because 640808565 - 2⁶ = 640808501 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11031 + ... + 37460.

It is an arithmetic number, because the mean of its divisors is an integer number (64154916).

Almost surely, 2^640808565 is an apocalyptic number.

It is an amenable number.

640808565 is a deficient number, since it is larger than the sum of its proper divisors (385670091).

640808565 is a wasteful number, since it uses less digits than its factorization.

640808565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49380.

The product of its (nonzero) digits is 230400, while the sum is 42.

The square root of 640808565 is about 25314.1969060841. The cubic root of 640808565 is about 862.1366400534.

The spelling of 640808565 in words is "six hundred forty million, eight hundred eight thousand, five hundred sixty-five".