638400555505 has 4 divisors (see below), whose sum is σ = 766080666612. Its totient is φ = 510720444400.

The previous prime is 638400555491. The next prime is 638400555571. The reversal of 638400555505 is 505555004836.

638400555505 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 376961616784 + 261438938721 = 613972^2 + 511311^2 .

It is not a de Polignac number, because 638400555505 - 2²⁷ = 638266337777 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63840055546 + ... + 63840055555.

It is an arithmetic number, because the mean of its divisors is an integer number (191520166653).

Almost surely, 2^638400555505 is an apocalyptic number.

It is an amenable number.

638400555505 is a deficient number, since it is larger than the sum of its proper divisors (127680111107).

638400555505 is a wasteful number, since it uses less digits than its factorization.

638400555505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127680111106.

The product of its (nonzero) digits is 1800000, while the sum is 46.

The spelling of 638400555505 in words is "six hundred thirty-eight billion, four hundred million, five hundred fifty-five thousand, five hundred five".