639943920 has 720 divisors, whose sum is σ = 2917500768. Its totient is φ = 123863040.

The previous prime is 639943901. The next prime is 639943939. The reversal of 639943920 is 29349936.

639943920 is a `hidden beast` number, since 639 + 9 + 4 + 3 + 9 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (639943901) and next prime (639943939).

It is a tau number, because it is divible by the number of its divisors (720).

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 143 ways as a sum of consecutive naturals, for example, 6597312 + ... + 6597408.

Almost surely, 2^639943920 is an apocalyptic number.

639943920 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 639943920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1458750384).

639943920 is an abundant number, since it is smaller than the sum of its proper divisors (2277556848).

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

639943920 is a wasteful number, since it uses less digits than its factorization.

639943920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 314928, while the sum is 45.

The square root of 639943920 is about 25297.1128787457. The cubic root of 639943920 is about 861.7487042989.

The spelling of 639943920 in words is "six hundred thirty-nine million, nine hundred forty-three thousand, nine hundred twenty".