638979408 has 160 divisors (see below), whose sum is σ = 1957374720. Its totient is φ = 198881280.

The previous prime is 638979403. The next prime is 638979421. The reversal of 638979408 is 804979836.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638979403) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 1226188 + ... + 1226708.

It is an arithmetic number, because the mean of its divisors is an integer number (12233592).

Almost surely, 2^638979408 is an apocalyptic number.

638979408 is a gapful number since it is divisible by the number (68) 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 638979408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (978687360).

638979408 is an abundant number, since it is smaller than the sum of its proper divisors (1318395312).

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

638979408 is a wasteful number, since it uses less digits than its factorization.

638979408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 722 (or 710 counting only the distinct ones).

The product of its (nonzero) digits is 2612736, while the sum is 54.

The square root of 638979408 is about 25278.0420127826. The cubic root of 638979408 is about 861.3155492137.

The spelling of 638979408 in words is "six hundred thirty-eight million, nine hundred seventy-nine thousand, four hundred eight".