638981 has 4 divisors (see below), whose sum is σ = 730272. Its totient is φ = 547692.

The previous prime is 638977. The next prime is 638993. The reversal of 638981 is 189836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638981 - 2² = 638977 is a prime.

It is a super-2 number, since 2×638981² = 816593436722, which contains 22 as substring.

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

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 638981.

It is not an unprimeable number, because it can be changed into a prime (638971) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45635 + ... + 45648.

It is an arithmetic number, because the mean of its divisors is an integer number (182568).

2⁶³⁸⁹⁸¹ is an apocalyptic number.

It is an amenable number.

638981 is a deficient number, since it is larger than the sum of its proper divisors (91291).

638981 is an equidigital number, since it uses as much as digits as its factorization.

638981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91290.

The product of its digits is 10368, while the sum is 35.

The square root of 638981 is about 799.3628712919. The cubic root of 638981 is about 86.1316264528.

The spelling of 638981 in words is "six hundred thirty-eight thousand, nine hundred eighty-one".