3121638921 has 24 divisors (see below), whose sum is σ = 4582371560. Its totient is φ = 2047389696.

The previous prime is 3121638887. The next prime is 3121638937. The reversal of 3121638921 is 1298361213.

3121638921 is a `hidden beast` number, since 3 + 12 + 1 + 638 + 9 + 2 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 969699600 + 2151939321 = 31140^2 + 46389^2 .

It is not a de Polignac number, because 3121638921 - 2¹¹ = 3121636873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3121638941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 262905 + ... + 274521.

Almost surely, 2^3121638921 is an apocalyptic number.

It is an amenable number.

3121638921 is a deficient number, since it is larger than the sum of its proper divisors (1460732639).

3121638921 is a wasteful number, since it uses less digits than its factorization.

3121638921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12105 (or 12102 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 3121638921 is about 55871.6289452885. The cubic root of 3121638921 is about 1461.4845288314.

The spelling of 3121638921 in words is "three billion, one hundred twenty-one million, six hundred thirty-eight thousand, nine hundred twenty-one".