639400544640 has 768 divisors, whose sum is σ = 2706791592960. Its totient is φ = 136857600000.

The previous prime is 639400544567. The next prime is 639400544659. The reversal of 639400544640 is 46445004936.

639400544640 is a `hidden beast` number, since 6 + 3 + 9 + 40 + 0 + 544 + 64 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 18927765 + ... + 18961515.

It is an arithmetic number, because the mean of its divisors is an integer number (3524468220).

Almost surely, 2^639400544640 is an apocalyptic number.

639400544640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639400544640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1353395796480).

639400544640 is an abundant number, since it is smaller than the sum of its proper divisors (2067391048320).

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

639400544640 is a wasteful number, since it uses less digits than its factorization.

639400544640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33823 (or 33808 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 45.

The spelling of 639400544640 in words is "six hundred thirty-nine billion, four hundred million, five hundred forty-four thousand, six hundred forty".