21231131221 has 12 divisors (see below), whose sum is σ = 22548341920. Its totient is φ = 19935478080.

The previous prime is 21231131219. The next prime is 21231131227. The reversal of 21231131221 is 12213113212.

It is not a de Polignac number, because 21231131221 - 2¹ = 21231131219 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231131227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 198856 + ... + 286366.

Almost surely, 2^21231131221 is an apocalyptic number.

It is an amenable number.

21231131221 is a deficient number, since it is larger than the sum of its proper divisors (1317210699).

21231131221 is an equidigital number, since it uses as much as digits as its factorization.

21231131221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87756 (or 87643 counting only the distinct ones).

The product of its digits is 144, while the sum is 19.

Adding to 21231131221 its reverse (12213113212), we get a palindrome (33444244433).

The spelling of 21231131221 in words is "twenty-one billion, two hundred thirty-one million, one hundred thirty-one thousand, two hundred twenty-one".