21012111220 has 24 divisors (see below), whose sum is σ = 44729894664. Its totient is φ = 8289709056.

The previous prime is 21012111167. The next prime is 21012111251. The reversal of 21012111220 is 2211121012.

It can be written as a sum of positive squares in 4 ways, for example, as 99480676 + 20912630544 = 9974^2 + 144612^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21012111220.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7194469 + ... + 7197388.

It is an arithmetic number, because the mean of its divisors is an integer number (1863745611).

Almost surely, 2^21012111220 is an apocalyptic number.

21012111220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21012111220 is an abundant number, since it is smaller than the sum of its proper divisors (23717783444).

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

21012111220 is a wasteful number, since it uses less digits than its factorization.

21012111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14391939 (or 14391937 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21012111220 its reverse (2211121012), we get a palindrome (23223232232).

The spelling of 21012111220 in words is "twenty-one billion, twelve million, one hundred eleven thousand, two hundred twenty".