21221211220 has 48 divisors (see below), whose sum is σ = 49746489408. Its totient is φ = 7537340160.

The previous prime is 21221211217. The next prime is 21221211227. The reversal of 21221211220 is 2211212212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21221211194 and 21221211203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221211227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1112169 + ... + 1131088.

It is an arithmetic number, because the mean of its divisors is an integer number (1036385196).

Almost surely, 2^21221211220 is an apocalyptic number.

21221211220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221211220 is an abundant number, since it is smaller than the sum of its proper divisors (28525278188).

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

21221211220 is a wasteful number, since it uses less digits than its factorization.

21221211220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2243320 (or 2243318 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21221211220 its reverse (2211212212), we get a palindrome (23432423432).

The spelling of 21221211220 in words is "twenty-one billion, two hundred twenty-one million, two hundred eleven thousand, two hundred twenty".