640187640 has 48 divisors (see below), whose sum is σ = 2080611000. Its totient is φ = 170716608.

The previous prime is 640187633. The next prime is 640187657. The reversal of 640187640 is 46781046.

640187640 is a `hidden beast` number, since 6 + 4 + 0 + 1 + 8 + 7 + 640 = 666.

640187640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 640187595 and 640187604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 888790 + ... + 889509.

Almost surely, 2^640187640 is an apocalyptic number.

640187640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640187640 is an abundant number, since it is smaller than the sum of its proper divisors (1440423360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640187640 is a wasteful number, since it uses less digits than its factorization.

640187640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1778316 (or 1778309 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The square root of 640187640 is about 25301.9295706869. The cubic root of 640187640 is about 861.8580882261.

The spelling of 640187640 in words is "six hundred forty million, one hundred eighty-seven thousand, six hundred forty".