31121221221 has 32 divisors (see below), whose sum is σ = 47333376000. Its totient is φ = 20199573360.

The previous prime is 31121221199. The next prime is 31121221289. The reversal of 31121221221 is 12212212113.

It is not a de Polignac number, because 31121221221 - 2¹⁰ = 31121220197 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31121221194 and 31121221203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31121221121) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 178180 + ... + 306578.

It is an arithmetic number, because the mean of its divisors is an integer number (1479168000).

Almost surely, 2^31121221221 is an apocalyptic number.

It is an amenable number.

31121221221 is a deficient number, since it is larger than the sum of its proper divisors (16212154779).

31121221221 is a wasteful number, since it uses less digits than its factorization.

31121221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128646 (or 128640 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

Adding to 31121221221 its reverse (12212212113), we get a palindrome (43333433334).

The spelling of 31121221221 in words is "thirty-one billion, one hundred twenty-one million, two hundred twenty-one thousand, two hundred twenty-one".