2172938379921 has 81 divisors (see below), whose sum is σ = 3269189336049. Its totient is φ = 1390785282432.

The previous prime is 2172938379881. The next prime is 2172938379959. The reversal of 2172938379921 is 1299738392712.

The square root of 2172938379921 is 1474089.

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

2172938379921 is a `hidden beast` number, since 2 + 172 + 9 + 3 + 8 + 379 + 92 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 185684289921 + 1987254090000 = 430911^2 + 1409700^2 .

It is a de Polignac number, because none of the positive numbers 2^k-2172938379921 is a prime.

It is a super-2 number, since 2×2172938379921² (a number of 25 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2172938375921) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 17109750960 + ... + 17109751086.

Almost surely, 2^{2172938379921} is an apocalyptic number.

2172938379921 is the 1474089-th square number.

2172938379921 is the 737045-th centered octagonal number.

It is an amenable number.

2172938379921 is a deficient number, since it is larger than the sum of its proper divisors (1096250956128).

2172938379921 is an frugal number, since it uses more digits than its factorization.

2172938379921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512 (or 256 counting only the distinct ones).

The product of its digits is 20575296, while the sum is 63.

The spelling of 2172938379921 in words is "two trillion, one hundred seventy-two billion, nine hundred thirty-eight million, three hundred seventy-nine thousand, nine hundred twenty-one".