638679220 has 24 divisors (see below), whose sum is σ = 1343913984. Its totient is φ = 254959776.

The previous prime is 638679199. The next prime is 638679221. The reversal of 638679220 is 22976836.

It is a super-2 number, since 2×638679220² = 815822292119616800, which contains 22 as substring.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638679221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21684 + ... + 41803.

It is an arithmetic number, because the mean of its divisors is an integer number (55996416).

Almost surely, 2^638679220 is an apocalyptic number.

It is an amenable number.

638679220 is an abundant number, since it is smaller than the sum of its proper divisors (705234764).

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

638679220 is a wasteful number, since it uses less digits than its factorization.

638679220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63999 (or 63997 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 43.

The square root of 638679220 is about 25272.1035926968. The cubic root of 638679220 is about 861.1806481048.

The spelling of 638679220 in words is "six hundred thirty-eight million, six hundred seventy-nine thousand, two hundred twenty".