638990 has 32 divisors (see below), whose sum is σ = 1296864. Its totient is φ = 224640.

The previous prime is 638977. The next prime is 638993. The reversal of 638990 is 99836.

It is a self number, because there is not a number n which added to its sum of digits gives 638990.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638993) by changing a digit.

638990 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3992 + ... + 4148.

It is an arithmetic number, because the mean of its divisors is an integer number (40527).

2⁶³⁸⁹⁹⁰ is an apocalyptic number.

638990 is an abundant number, since it is smaller than the sum of its proper divisors (657874).

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

638990 is a wasteful number, since it uses less digits than its factorization.

638990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 638990 is about 799.3685007554. The cubic root of 638990 is about 86.1320308368.

The spelling of 638990 in words is "six hundred thirty-eight thousand, nine hundred ninety".