638936820 has 36 divisors (see below), whose sum is σ = 1938108900. Its totient is φ = 170383104.

The previous prime is 638936819. The next prime is 638936839. The reversal of 638936820 is 28639836.

638936820 is a `hidden beast` number, since 638 + 9 + 3 + 6 + 8 + 2 + 0 = 666.

638936820 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 364504464 + 274432356 = 19092^2 + 16566^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1774645 + ... + 1775004.

Almost surely, 2^638936820 is an apocalyptic number.

638936820 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

638936820 is an abundant number, since it is smaller than the sum of its proper divisors (1299172080).

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

638936820 is a wasteful number, since it uses less digits than its factorization.

638936820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3549664 (or 3549659 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 638936820 is about 25277.1996075515. The cubic root of 638936820 is about 861.2964132180.

The spelling of 638936820 in words is "six hundred thirty-eight million, nine hundred thirty-six thousand, eight hundred twenty".