639919764 has 120 divisors (see below), whose sum is σ = 1833585600. Its totient is φ = 193000320.

The previous prime is 639919691. The next prime is 639919783. The reversal of 639919764 is 467919936.

639919764 is a `hidden beast` number, since 6 + 399 + 197 + 64 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 639919764.

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, 1457457 + ... + 1457895.

It is an arithmetic number, because the mean of its divisors is an integer number (15279880).

Almost surely, 2^639919764 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639919764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (916792800).

639919764 is an abundant number, since it is smaller than the sum of its proper divisors (1193665836).

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

639919764 is a wasteful number, since it uses less digits than its factorization.

639919764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875 (or 864 counting only the distinct ones).

The product of its digits is 2204496, while the sum is 54.

The square root of 639919764 is about 25296.6354284517. The cubic root of 639919764 is about 861.7378613365.

The spelling of 639919764 in words is "six hundred thirty-nine million, nine hundred nineteen thousand, seven hundred sixty-four".