638925988 has 6 divisors (see below), whose sum is σ = 1118120486. Its totient is φ = 319462992.

The previous prime is 638925983. The next prime is 638926007. The reversal of 638925988 is 889529836.

It can be written as a sum of positive squares in only one way, i.e., 638673984 + 252004 = 25272^2 + 502^2 .

It is a super-2 number, since 2×638925988² = 816452836283552288, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (638925983) 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 as a sum of consecutive naturals, namely, 79865745 + ... + 79865752.

Almost surely, 2^638925988 is an apocalyptic number.

It is an amenable number.

638925988 is a deficient number, since it is larger than the sum of its proper divisors (479194498).

638925988 is a wasteful number, since it uses less digits than its factorization.

638925988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159731501 (or 159731499 counting only the distinct ones).

The product of its digits is 7464960, while the sum is 58.

The square root of 638925988 is about 25276.9853424019. The cubic root of 638925988 is about 861.2915459577.

The spelling of 638925988 in words is "six hundred thirty-eight million, nine hundred twenty-five thousand, nine hundred eighty-eight".