638131937 has 4 divisors (see below), whose sum is σ = 638444820. Its totient is φ = 637819056.

The previous prime is 638131927. The next prime is 638131939. The reversal of 638131937 is 739131836.

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

It can be written as a sum of positive squares in 2 ways, for example, as 373223761 + 264908176 = 19319^2 + 16276^2 .

It is a cyclic number.

It is not a de Polignac number, because 638131937 - 2²⁰ = 637083361 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638131894 and 638131903.

It is not an unprimeable number, because it can be changed into a prime (638131939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 153362 + ... + 157467.

It is an arithmetic number, because the mean of its divisors is an integer number (159611205).

Almost surely, 2^638131937 is an apocalyptic number.

It is an amenable number.

638131937 is a deficient number, since it is larger than the sum of its proper divisors (312883).

638131937 is a wasteful number, since it uses less digits than its factorization.

638131937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312882.

The product of its digits is 81648, while the sum is 41.

The square root of 638131937 is about 25261.2734635449. The cubic root of 638131937 is about 860.9345964619.

The spelling of 638131937 in words is "six hundred thirty-eight million, one hundred thirty-one thousand, nine hundred thirty-seven".