638643620 has 12 divisors (see below), whose sum is σ = 1341151644. Its totient is φ = 255457440.

The previous prime is 638643613. The next prime is 638643667. The reversal of 638643620 is 26346836.

It can be written as a sum of positive squares in 2 ways, for example, as 68293696 + 570349924 = 8264^2 + 23882^2 .

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 15966071 + ... + 15966110.

It is an arithmetic number, because the mean of its divisors is an integer number (111762637).

Almost surely, 2^638643620 is an apocalyptic number.

It is an amenable number.

638643620 is an abundant number, since it is smaller than the sum of its proper divisors (702508024).

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

638643620 is a wasteful number, since it uses less digits than its factorization.

638643620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31932190 (or 31932188 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 38.

The square root of 638643620 is about 25271.3992489534. The cubic root of 638643620 is about 861.1646470620.

The spelling of 638643620 in words is "six hundred thirty-eight million, six hundred forty-three thousand, six hundred twenty".