638977640 has 192 divisors, whose sum is σ = 1796567040. Its totient is φ = 203212800.

The previous prime is 638977639. The next prime is 638977681. The reversal of 638977640 is 46779836.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4231565 + ... + 4231715.

It is an arithmetic number, because the mean of its divisors is an integer number (9357120).

Almost surely, 2^638977640 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 638977640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (898283520).

638977640 is an abundant number, since it is smaller than the sum of its proper divisors (1157589400).

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

638977640 is a wasteful number, since it uses less digits than its factorization.

638977640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320 (or 309 counting only the distinct ones).

The product of its (nonzero) digits is 1524096, while the sum is 50.

The square root of 638977640 is about 25278.0070416954. The cubic root of 638977640 is about 861.3147548181.

The spelling of 638977640 in words is "six hundred thirty-eight million, nine hundred seventy-seven thousand, six hundred forty".