638168644 has 27 divisors (see below), whose sum is σ = 1187952157. Its totient is φ = 299910464.

The previous prime is 638168617. The next prime is 638168647. The reversal of 638168644 is 446861836.

The square root of 638168644 is 25262.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 496844100 + 141324544 = 22290^2 + 11888^2 .

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638168594 and 638168603.

It is not an unprimeable number, because it can be changed into a prime (638168647) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 858537 + ... + 859279.

Almost surely, 2^638168644 is an apocalyptic number.

638168644 is the 25262-nd square number.

It is an amenable number.

638168644 is a deficient number, since it is larger than the sum of its proper divisors (549783513).

638168644 is an equidigital number, since it uses as much as digits as its factorization.

638168644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1524 (or 762 counting only the distinct ones).

The product of its digits is 663552, while the sum is 46.

The cubic root of 638168644 is about 860.9511038739.

The spelling of 638168644 in words is "six hundred thirty-eight million, one hundred sixty-eight thousand, six hundred forty-four".