640634645 has 16 divisors (see below), whose sum is σ = 878999808. Its totient is φ = 439084800.

The previous prime is 640634639. The next prime is 640634677. The reversal of 640634645 is 546436046.

It is a happy number.

It is not a de Polignac number, because 640634645 - 2¹⁶ = 640569109 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640634599 and 640634608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 126920 + ... + 131870.

It is an arithmetic number, because the mean of its divisors is an integer number (54937488).

Almost surely, 2^640634645 is an apocalyptic number.

It is an amenable number.

640634645 is a deficient number, since it is larger than the sum of its proper divisors (238365163).

640634645 is a wasteful number, since it uses less digits than its factorization.

640634645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8660.

The product of its (nonzero) digits is 207360, while the sum is 38.

The square root of 640634645 is about 25310.7614464678. The cubic root of 640634645 is about 862.0586363251.

The spelling of 640634645 in words is "six hundred forty million, six hundred thirty-four thousand, six hundred forty-five".