638173213 has 4 divisors (see below), whose sum is σ = 638453340. Its totient is φ = 637893088.

The previous prime is 638173201. The next prime is 638173229. The reversal of 638173213 is 312371836.

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 528908004 + 109265209 = 22998^2 + 10453^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638173213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638174213) 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, 136618 + ... + 141211.

It is an arithmetic number, because the mean of its divisors is an integer number (159613335).

Almost surely, 2^638173213 is an apocalyptic number.

It is an amenable number.

638173213 is a deficient number, since it is larger than the sum of its proper divisors (280127).

638173213 is a wasteful number, since it uses less digits than its factorization.

638173213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280126.

The product of its digits is 18144, while the sum is 34.

The square root of 638173213 is about 25262.0904321079. The cubic root of 638173213 is about 860.9531585430.

The spelling of 638173213 in words is "six hundred thirty-eight million, one hundred seventy-three thousand, two hundred thirteen".