638611555121 has 4 divisors (see below), whose sum is σ = 638614241892. Its totient is φ = 638608868352.

The previous prime is 638611555093. The next prime is 638611555151. The reversal of 638611555121 is 121555116836.

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 94947178225 + 543664376896 = 308135^2 + 737336^2 .

It is a cyclic number.

It is not a de Polignac number, because 638611555121 - 2²⁶ = 638544446257 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638611555151) 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, 948080 + ... + 1475153.

It is an arithmetic number, because the mean of its divisors is an integer number (159653560473).

Almost surely, 2^638611555121 is an apocalyptic number.

It is an amenable number.

638611555121 is a deficient number, since it is larger than the sum of its proper divisors (2686771).

638611555121 is a wasteful number, since it uses less digits than its factorization.

638611555121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2686770.

The product of its digits is 216000, while the sum is 44.

The spelling of 638611555121 in words is "six hundred thirty-eight billion, six hundred eleven million, five hundred fifty-five thousand, one hundred twenty-one".