638691790 has 16 divisors (see below), whose sum is σ = 1254158640. Its totient is φ = 232251520.

The previous prime is 638691721. The next prime is 638691799. The reversal of 638691790 is 97196836.

It is a super-2 number, since 2×638691790² = 815854405226808200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638691799) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2903035 + ... + 2903254.

It is an arithmetic number, because the mean of its divisors is an integer number (78384915).

Almost surely, 2^638691790 is an apocalyptic number.

638691790 is a deficient number, since it is larger than the sum of its proper divisors (615466850).

638691790 is a wasteful number, since it uses less digits than its factorization.

638691790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5806307.

The product of its (nonzero) digits is 489888, while the sum is 49.

The square root of 638691790 is about 25272.3522846608. The cubic root of 638691790 is about 861.1862977692.

The spelling of 638691790 in words is "six hundred thirty-eight million, six hundred ninety-one thousand, seven hundred ninety".