13639438171921 has 3 divisors (see below), whose sum is σ = 13639441865083. Its totient is φ = 13639434478760.

The previous prime is 13639438171913. The next prime is 13639438171927. The reversal of 13639438171921 is 12917183493631.

It is a happy number.

The square root of 13639438171921 is 3693161.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 8551887258321 + 5087550913600 = 2924361^2 + 2255560^2 .

It is not a de Polignac number, because 13639438171921 - 2³ = 13639438171913 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13639438171927) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1846581 + ... + 5539741.

Almost surely, 2^{13639438171921} is an apocalyptic number.

13639438171921 is the 3693161-st square number.

13639438171921 is the 1846581-st centered octagonal number.

It is an amenable number.

13639438171921 is a deficient number, since it is larger than the sum of its proper divisors (3693162).

13639438171921 is an frugal number, since it uses more digits than its factorization.

13639438171921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7386322 (or 3693161 counting only the distinct ones).

The product of its digits is 5878656, while the sum is 58.

The spelling of 13639438171921 in words is "thirteen trillion, six hundred thirty-nine billion, four hundred thirty-eight million, one hundred seventy-one thousand, nine hundred twenty-one".