21121912 has 64 divisors (see below), whose sum is σ = 48844800. Its totient is φ = 8379360.

The previous prime is 21121909. The next prime is 21121913. The reversal of 21121912 is 21912112.

It is a happy number.

It is a super-2 number, since 2×21121912² = 892270333071488, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21121912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121913) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 681337 + ... + 681367.

It is an arithmetic number, because the mean of its divisors is an integer number (763200).

Almost surely, 2^21121912 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21121912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24422400).

21121912 is an abundant number, since it is smaller than the sum of its proper divisors (27722888).

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

21121912 is an equidigital number, since it uses as much as digits as its factorization.

21121912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113 (or 63 counting only the distinct ones).

The product of its digits is 72, while the sum is 19.

The square root of 21121912 is about 4595.8581353214. The cubic root of 21121912 is about 276.4252703182.

The spelling of 21121912 in words is "twenty-one million, one hundred twenty-one thousand, nine hundred twelve".