639687442 has 4 divisors (see below), whose sum is σ = 959531166. Its totient is φ = 319843720.

The previous prime is 639687401. The next prime is 639687473. The reversal of 639687442 is 244786936.

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., 565916521 + 73770921 = 23789^2 + 8589^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159921859 + ... + 159921862.

Almost surely, 2^639687442 is an apocalyptic number.

639687442 is a deficient number, since it is larger than the sum of its proper divisors (319843724).

639687442 is a wasteful number, since it uses less digits than its factorization.

639687442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319843723.

The product of its digits is 1741824, while the sum is 49.

The square root of 639687442 is about 25292.0430570565. The cubic root of 639687442 is about 861.6335644610.

The spelling of 639687442 in words is "six hundred thirty-nine million, six hundred eighty-seven thousand, four hundred forty-two".