638632426644 has 36 divisors (see below), whose sum is σ = 1709280908244. Its totient is φ = 200355270912.

The previous prime is 638632426573. The next prime is 638632426697. The reversal of 638632426644 is 446624236836.

638632426644 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 408819572100 + 229812854544 = 639390^2 + 479388^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×638632426644² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 521757907 + ... + 521759130.

It is an arithmetic number, because the mean of its divisors is an integer number (47480025229).

Almost surely, 2^638632426644 is an apocalyptic number.

It is an amenable number.

638632426644 is an abundant number, since it is smaller than the sum of its proper divisors (1070648481600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

638632426644 is a wasteful number, since it uses less digits than its factorization.

638632426644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1043517064 (or 1043517059 counting only the distinct ones).

The product of its digits is 23887872, while the sum is 54.

The spelling of 638632426644 in words is "six hundred thirty-eight billion, six hundred thirty-two million, four hundred twenty-six thousand, six hundred forty-four".