638988 has 24 divisors (see below), whose sum is σ = 1704192. Its totient is φ = 182544.

The previous prime is 638977. The next prime is 638993. The reversal of 638988 is 889836.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 638988.

It is an unprimeable number.

638988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3720 + ... + 3887.

It is an arithmetic number, because the mean of its divisors is an integer number (71008).

2⁶³⁸⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

638988 is an abundant number, since it is smaller than the sum of its proper divisors (1065204).

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

638988 is a wasteful number, since it uses less digits than its factorization.

638988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7621 (or 7619 counting only the distinct ones).

The product of its digits is 82944, while the sum is 42.

The square root of 638988 is about 799.3672497670. The cubic root of 638988 is about 86.1319409740.

The spelling of 638988 in words is "six hundred thirty-eight thousand, nine hundred eighty-eight".