638644355 has 16 divisors (see below), whose sum is σ = 812169504. Its totient is φ = 480437760.

The previous prime is 638644339. The next prime is 638644387. The reversal of 638644355 is 553446836.

It is a happy number.

It is not a de Polignac number, because 638644355 - 2⁴ = 638644339 is a prime.

It is a super-2 number, since 2×638644355² = 815733224346732050, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120920 + ... + 126090.

It is an arithmetic number, because the mean of its divisors is an integer number (50760594).

Almost surely, 2^638644355 is an apocalyptic number.

638644355 is a deficient number, since it is larger than the sum of its proper divisors (173525149).

638644355 is a wasteful number, since it uses less digits than its factorization.

638644355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6646.

The product of its digits is 1036800, while the sum is 44.

The square root of 638644355 is about 25271.4137910802. The cubic root of 638644355 is about 861.1649774266.

The spelling of 638644355 in words is "six hundred thirty-eight million, six hundred forty-four thousand, three hundred fifty-five".