21231231220 has 96 divisors (see below), whose sum is σ = 46286132256. Its totient is φ = 8174131200.

The previous prime is 21231231211. The next prime is 21231231221. The reversal of 21231231220 is 2213213212.

It can be written as a sum of positive squares in 16 ways, for example, as 2528480656 + 18702750564 = 50284^2 + 136758^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231231221) 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 31 ways as a sum of consecutive naturals, for example, 39244150 + ... + 39244690.

It is an arithmetic number, because the mean of its divisors is an integer number (482147211).

Almost surely, 2^21231231220 is an apocalyptic number.

21231231220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21231231220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23143066128).

21231231220 is an abundant number, since it is smaller than the sum of its proper divisors (25054901036).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21231231220 is a wasteful number, since it uses less digits than its factorization.

21231231220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1061 (or 1059 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21231231220 its reverse (2213213212), we get a palindrome (23444444432).

The spelling of 21231231220 in words is "twenty-one billion, two hundred thirty-one million, two hundred thirty-one thousand, two hundred twenty".