21221323220 has 12 divisors (see below), whose sum is σ = 44564778804. Its totient is φ = 8488529280.

The previous prime is 21221323217. The next prime is 21221323237. The reversal of 21221323220 is 2232312212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 14334315076 + 6887008144 = 119726^2 + 82988^2 .

It is a super-2 number, since 2×21221323220² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1061066161 = 21221323220 / (2 + 1 + 2 + 2 + 1 + 3 + 2 + 3 + 2 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 21221323192 and 21221323201.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 530533061 + ... + 530533100.

It is an arithmetic number, because the mean of its divisors is an integer number (3713731567).

Almost surely, 2^21221323220 is an apocalyptic number.

21221323220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221323220 is an abundant number, since it is smaller than the sum of its proper divisors (23343455584).

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

21221323220 is a wasteful number, since it uses less digits than its factorization.

21221323220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1061066170 (or 1061066168 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

Adding to 21221323220 its reverse (2232312212), we get a palindrome (23453635432).

The spelling of 21221323220 in words is "twenty-one billion, two hundred twenty-one million, three hundred twenty-three thousand, two hundred twenty".