638637994 has 8 divisors (see below), whose sum is σ = 1008375840. Its totient is φ = 302512716.

The previous prime is 638637983. The next prime is 638638003. The reversal of 638637994 is 499736836.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8403094 + ... + 8403169.

It is an arithmetic number, because the mean of its divisors is an integer number (126046980).

Almost surely, 2^638637994 is an apocalyptic number.

638637994 is a deficient number, since it is larger than the sum of its proper divisors (369737846).

638637994 is a wasteful number, since it uses less digits than its factorization.

638637994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16806284.

The product of its digits is 5878656, while the sum is 55.

The square root of 638637994 is about 25271.2879371036. The cubic root of 638637994 is about 861.1621183034.

The spelling of 638637994 in words is "six hundred thirty-eight million, six hundred thirty-seven thousand, nine hundred ninety-four".