21122221220 has 12 divisors (see below), whose sum is σ = 44356664604. Its totient is φ = 8448888480.

The previous prime is 21122221193. The next prime is 21122221249. The reversal of 21122221220 is 2212222112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 11483694244 + 9638526976 = 107162^2 + 98176^2 .

It is a super-2 number, since 2×21122221220² (a number of 21 digits) contains 22 as substring.

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, 528055511 + ... + 528055550.

It is an arithmetic number, because the mean of its divisors is an integer number (3696388717).

Almost surely, 2^21122221220 is an apocalyptic number.

21122221220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21122221220 is an abundant number, since it is smaller than the sum of its proper divisors (23234443384).

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

21122221220 is a wasteful number, since it uses less digits than its factorization.

21122221220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1056111070 (or 1056111068 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21122221220 its reverse (2212222112), we get a palindrome (23334443332).

The spelling of 21122221220 in words is "twenty-one billion, one hundred twenty-two million, two hundred twenty-one thousand, two hundred twenty".