640956405 has 32 divisors (see below), whose sum is σ = 1075887360. Its totient is φ = 325391360.

The previous prime is 640956377. The next prime is 640956419. The reversal of 640956405 is 504659046.

It is not a de Polignac number, because 640956405 - 2⁸ = 640956149 is a prime.

It is a super-2 number, since 2×640956405² = 821650226221048050, which contains 22 as substring.

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 31 ways as a sum of consecutive naturals, for example, 20509 + ... + 41261.

It is an arithmetic number, because the mean of its divisors is an integer number (33621480).

Almost surely, 2^640956405 is an apocalyptic number.

It is an amenable number.

640956405 is a deficient number, since it is larger than the sum of its proper divisors (434930955).

640956405 is a wasteful number, since it uses less digits than its factorization.

640956405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20861.

The product of its (nonzero) digits is 129600, while the sum is 39.

The square root of 640956405 is about 25317.1168382184. The cubic root of 640956405 is about 862.2029357134.

It can be divided in two parts, 64095 and 6405, that added together give a triangular number (70500 = T₃₇₅).

The spelling of 640956405 in words is "six hundred forty million, nine hundred fifty-six thousand, four hundred five".