639545840 has 40 divisors (see below), whose sum is σ = 1512157680. Its totient is φ = 251480576.

The previous prime is 639545827. The next prime is 639545857. The reversal of 639545840 is 48545936.

639545840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×639545840² = 818037762922611200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 639545791 and 639545800.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 63029 + ... + 72468.

It is an arithmetic number, because the mean of its divisors is an integer number (37803942).

Almost surely, 2^639545840 is an apocalyptic number.

It is an amenable number.

639545840 is an abundant number, since it is smaller than the sum of its proper divisors (872611840).

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

639545840 is a wasteful number, since it uses less digits than its factorization.

639545840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135569 (or 135563 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 44.

The square root of 639545840 is about 25289.2435632227. The cubic root of 639545840 is about 861.5699823469.

The spelling of 639545840 in words is "six hundred thirty-nine million, five hundred forty-five thousand, eight hundred forty".