21131221320 has 192 divisors, whose sum is σ = 75258892800. Its totient is φ = 5099535360.

The previous prime is 21131221303. The next prime is 21131221327. The reversal of 21131221320 is 2312213112.

21131221320 is a `hidden beast` number, since 2 + 11 + 312 + 21 + 320 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21131221293 and 21131221302.

It is not an unprimeable number, because it can be changed into a prime (21131221327) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 871116 + ... + 895044.

It is an arithmetic number, because the mean of its divisors is an integer number (391973400).

Almost surely, 2^21131221320 is an apocalyptic number.

21131221320 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 21131221320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37629446400).

21131221320 is an abundant number, since it is smaller than the sum of its proper divisors (54127671480).

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

21131221320 is a wasteful number, since it uses less digits than its factorization.

21131221320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24180 (or 24173 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 21131221320 its reverse (2312213112), we get a palindrome (23443434432).

The spelling of 21131221320 in words is "twenty-one billion, one hundred thirty-one million, two hundred twenty-one thousand, three hundred twenty".