638866540 has 24 divisors (see below), whose sum is σ = 1444821840. Its totient is φ = 235889088.

The previous prime is 638866513. The next prime is 638866577. The reversal of 638866540 is 45668836.

It is a hoax number, since the sum of its digits (46) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1228330 + ... + 1228849.

It is an arithmetic number, because the mean of its divisors is an integer number (60200910).

Almost surely, 2^638866540 is an apocalyptic number.

It is an amenable number.

638866540 is an abundant number, since it is smaller than the sum of its proper divisors (805955300).

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

638866540 is a wasteful number, since it uses less digits than its factorization.

638866540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2457201 (or 2457199 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 46.

The square root of 638866540 is about 25275.8093836775. The cubic root of 638866540 is about 861.2648325621.

The spelling of 638866540 in words is "six hundred thirty-eight million, eight hundred sixty-six thousand, five hundred forty".