21121220220 has 24 divisors (see below), whose sum is σ = 59139416784. Its totient is φ = 5632325376.

The previous prime is 21121220177. The next prime is 21121220227. The reversal of 21121220220 is 2202212112.

It is a super-2 number, since 2×21121220220² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21121220220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121220227) 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, 176010109 + ... + 176010228.

It is an arithmetic number, because the mean of its divisors is an integer number (2464142366).

Almost surely, 2^21121220220 is an apocalyptic number.

21121220220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121220220 is an abundant number, since it is smaller than the sum of its proper divisors (38018196564).

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

21121220220 is a wasteful number, since it uses less digits than its factorization.

21121220220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 352020349 (or 352020347 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21121220220 its reverse (2202212112), we get a palindrome (23323432332).

The spelling of 21121220220 in words is "twenty-one billion, one hundred twenty-one million, two hundred twenty thousand, two hundred twenty".