31972177921 has 4 divisors (see below), whose sum is σ = 32156988372. Its totient is φ = 31787367472.

The previous prime is 31972177891. The next prime is 31972177931. The reversal of 31972177921 is 12977127913.

It is a happy number.

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 13389035521 + 18583142400 = 115711^2 + 136320^2 .

It is a cyclic number.

It is not a de Polignac number, because 31972177921 - 2¹⁹ = 31971653633 is a prime.

It is a super-2 number, since 2×31972177921² (a number of 22 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (49) 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 not an unprimeable number, because it can be changed into a prime (31972177931) 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, 92404966 + ... + 92405311.

It is an arithmetic number, because the mean of its divisors is an integer number (8039247093).

Almost surely, 2^31972177921 is an apocalyptic number.

It is an amenable number.

31972177921 is a deficient number, since it is larger than the sum of its proper divisors (184810451).

31972177921 is a wasteful number, since it uses less digits than its factorization.

31972177921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 184810450.

The product of its digits is 333396, while the sum is 49.

The spelling of 31972177921 in words is "thirty-one billion, nine hundred seventy-two million, one hundred seventy-seven thousand, nine hundred twenty-one".