638633465621 has 4 divisors (see below), whose sum is σ = 638967306252. Its totient is φ = 638299624992.

The previous prime is 638633465609. The next prime is 638633465671. The reversal of 638633465621 is 126564336836.

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 570009900100 + 68623565521 = 754990^2 + 261961^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638633465621 is a prime.

It is a super-2 number, since 2×638633465621² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638633465671) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166917446 + ... + 166921271.

It is an arithmetic number, because the mean of its divisors is an integer number (159741826563).

Almost surely, 2^638633465621 is an apocalyptic number.

It is an amenable number.

638633465621 is a deficient number, since it is larger than the sum of its proper divisors (333840631).

638633465621 is a wasteful number, since it uses less digits than its factorization.

638633465621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333840630.

The product of its digits is 11197440, while the sum is 53.

The spelling of 638633465621 in words is "six hundred thirty-eight billion, six hundred thirty-three million, four hundred sixty-five thousand, six hundred twenty-one".