21101211220 has 24 divisors (see below), whose sum is σ = 44769378024. Its totient is φ = 8353468416.

The previous prime is 21101211193. The next prime is 21101211221. The reversal of 21101211220 is 2211210112.

It can be written as a sum of positive squares in 4 ways, for example, as 5391684 + 21095819536 = 2322^2 + 145244^2 .

It is a super-2 number, since 2×21101211220² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21101211220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101211221) 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, 5436517 + ... + 5440396.

It is an arithmetic number, because the mean of its divisors is an integer number (1865390751).

Almost surely, 2^21101211220 is an apocalyptic number.

21101211220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101211220 is an abundant number, since it is smaller than the sum of its proper divisors (23668166804).

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

21101211220 is a wasteful number, since it uses less digits than its factorization.

21101211220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10877019 (or 10877017 counting only the distinct ones).

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

Adding to 21101211220 its reverse (2211210112), we get a palindrome (23312421332).

The spelling of 21101211220 in words is "twenty-one billion, one hundred one million, two hundred eleven thousand, two hundred twenty".