21002221220 has 24 divisors (see below), whose sum is σ = 44328554424. Its totient is φ = 8358242816.

The previous prime is 21002221199. The next prime is 21002221223. The reversal of 21002221220 is 2212220012.

It can be written as a sum of positive squares in 4 ways, for example, as 8943106624 + 12059114596 = 94568^2 + 109814^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21002221195 and 21002221204.

It is not an unprimeable number, because it can be changed into a prime (21002221223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2661317 + ... + 2669196.

It is an arithmetic number, because the mean of its divisors is an integer number (1847023101).

Almost surely, 2^21002221220 is an apocalyptic number.

21002221220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21002221220 is an abundant number, since it is smaller than the sum of its proper divisors (23326333204).

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

21002221220 is a wasteful number, since it uses less digits than its factorization.

21002221220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5330719 (or 5330717 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

Adding to 21002221220 its reverse (2212220012), we get a palindrome (23214441232).

The spelling of 21002221220 in words is "twenty-one billion, two million, two hundred twenty-one thousand, two hundred twenty".