640090856 has 8 divisors (see below), whose sum is σ = 1200170370. Its totient is φ = 320045424.

The previous prime is 640090807. The next prime is 640090879. The reversal of 640090856 is 658090046.

It can be written as a sum of positive squares in only one way, i.e., 603488356 + 36602500 = 24566^2 + 6050^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40005671 + ... + 40005686.

Almost surely, 2^640090856 is an apocalyptic number.

It is an amenable number.

640090856 is a deficient number, since it is larger than the sum of its proper divisors (560079514).

640090856 is a wasteful number, since it uses less digits than its factorization.

640090856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80011363 (or 80011359 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 38.

The square root of 640090856 is about 25300.0169169904. The cubic root of 640090856 is about 861.8146539411.

The spelling of 640090856 in words is "six hundred forty million, ninety thousand, eight hundred fifty-six".