638531 has 4 divisors (see below), whose sum is σ = 647352. Its totient is φ = 629712.

The previous prime is 638527. The next prime is 638567. The reversal of 638531 is 135836.

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 638531 - 2² = 638527 is a prime.

It is a super-2 number, since 2×638531² = 815443675922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 638531.

It is not an unprimeable number, because it can be changed into a prime (638501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4301 + ... + 4446.

It is an arithmetic number, because the mean of its divisors is an integer number (161838).

2⁶³⁸⁵³¹ is an apocalyptic number.

638531 is a deficient number, since it is larger than the sum of its proper divisors (8821).

638531 is an equidigital number, since it uses as much as digits as its factorization.

638531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8820.

The product of its digits is 2160, while the sum is 26.

The square root of 638531 is about 799.0813475485. The cubic root of 638531 is about 86.1114024116. Note that the first 3 decimals are identical.

The spelling of 638531 in words is "six hundred thirty-eight thousand, five hundred thirty-one".