21121001220 has 96 divisors (see below), whose sum is σ = 66596253696. Its totient is φ = 4955068800.

The previous prime is 21121001207. The next prime is 21121001233. The reversal of 21121001220 is 2210012112.

It is an interprime number because it is at equal distance from previous prime (21121001207) and next prime (21121001233).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21121001196 and 21121001205.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 495694 + ... + 536613.

It is an arithmetic number, because the mean of its divisors is an integer number (693710976).

Almost surely, 2^21121001220 is an apocalyptic number.

21121001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121001220 is an abundant number, since it is smaller than the sum of its proper divisors (45475252476).

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

21121001220 is a wasteful number, since it uses less digits than its factorization.

21121001220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1032361 (or 1032359 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21121001220 its reverse (2210012112), we get a palindrome (23331013332).

The spelling of 21121001220 in words is "twenty-one billion, one hundred twenty-one million, one thousand, two hundred twenty".