639368640 has 280 divisors, whose sum is σ = 2409791472. Its totient is φ = 160358400.

The previous prime is 639368617. The next prime is 639368669. The reversal of 639368640 is 46863936.

639368640 is a `hidden beast` number, since 639 + 3 + 6 + 8 + 6 + 4 + 0 = 666.

It is a super-4 number, since 4×639368640⁴ (a number of 36 digits) contains 4444 as substring.

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 39 ways as a sum of consecutive naturals, for example, 439915 + ... + 441365.

Almost surely, 2^639368640 is an apocalyptic number.

639368640 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 639368640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1204895736).

639368640 is an abundant number, since it is smaller than the sum of its proper divisors (1770422832).

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

639368640 is a wasteful number, since it uses less digits than its factorization.

639368640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1497 (or 1478 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 45.

The square root of 639368640 is about 25285.7398547086. The cubic root of 639368640 is about 861.4904028006.

The spelling of 639368640 in words is "six hundred thirty-nine million, three hundred sixty-eight thousand, six hundred forty".