638987 has 4 divisors (see below), whose sum is σ = 640680. Its totient is φ = 637296.

The previous prime is 638977. The next prime is 638993. The reversal of 638987 is 789836.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 638987 - 2⁴ = 638971 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 638987.

It is not an unprimeable number, because it can be changed into a prime (638977) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 8 + ... + 1130.

It is an arithmetic number, because the mean of its divisors is an integer number (160170).

2⁶³⁸⁹⁸⁷ is an apocalyptic number.

638987 is a deficient number, since it is larger than the sum of its proper divisors (1693).

638987 is a wasteful number, since it uses less digits than its factorization.

638987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1692.

The product of its digits is 72576, while the sum is 41.

The square root of 638987 is about 799.3666242720. The cubic root of 638987 is about 86.1318960425.

The spelling of 638987 in words is "six hundred thirty-eight thousand, nine hundred eighty-seven".