638791042 has 4 divisors (see below), whose sum is σ = 958186566. Its totient is φ = 319395520.

The previous prime is 638791037. The next prime is 638791057. The reversal of 638791042 is 240197836.

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

It can be written as a sum of positive squares in only one way, i.e., 526197721 + 112593321 = 22939^2 + 10611^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 638790986 and 638791004.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159697759 + ... + 159697762.

Almost surely, 2^638791042 is an apocalyptic number.

638791042 is a deficient number, since it is larger than the sum of its proper divisors (319395524).

638791042 is a wasteful number, since it uses less digits than its factorization.

638791042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319395523.

The product of its (nonzero) digits is 72576, while the sum is 40.

The square root of 638791042 is about 25274.3158562205. The cubic root of 638791042 is about 861.2309045924.

The spelling of 638791042 in words is "six hundred thirty-eight million, seven hundred ninety-one thousand, forty-two".