638323918 has 4 divisors (see below), whose sum is σ = 957485880. Its totient is φ = 319161958.

The previous prime is 638323913. The next prime is 638323919. The reversal of 638323918 is 819323836.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638323913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159580978 + ... + 159580981.

It is an arithmetic number, because the mean of its divisors is an integer number (239371470).

Almost surely, 2^638323918 is an apocalyptic number.

638323918 is a deficient number, since it is larger than the sum of its proper divisors (319161962).

638323918 is a wasteful number, since it uses less digits than its factorization.

638323918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319161961.

The product of its digits is 186624, while the sum is 43.

The square root of 638323918 is about 25265.0730851902. The cubic root of 638323918 is about 861.0209247497.

The spelling of 638323918 in words is "six hundred thirty-eight million, three hundred twenty-three thousand, nine hundred eighteen".