638634451765 has 4 divisors (see below), whose sum is σ = 766361342124. Its totient is φ = 510907561408.

The previous prime is 638634451727. The next prime is 638634451771. The reversal of 638634451765 is 567154436836.

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 160225679524 + 478408772241 = 400282^2 + 691671^2 .

It is a cyclic number.

It is not a de Polignac number, because 638634451765 - 2⁹ = 638634451253 is a prime.

It is a super-2 number, since 2×638634451765² (a number of 24 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent 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, 63863445172 + ... + 63863445181.

It is an arithmetic number, because the mean of its divisors is an integer number (191590335531).

Almost surely, 2^638634451765 is an apocalyptic number.

It is an amenable number.

638634451765 is a deficient number, since it is larger than the sum of its proper divisors (127726890359).

638634451765 is a wasteful number, since it uses less digits than its factorization.

638634451765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127726890358.

The product of its digits is 43545600, while the sum is 58.

The spelling of 638634451765 in words is "six hundred thirty-eight billion, six hundred thirty-four million, four hundred fifty-one thousand, seven hundred sixty-five".