21021120 has 140 divisors (see below), whose sum is σ = 74868024. Its totient is φ = 5598720.

The previous prime is 21021107. The next prime is 21021127. The reversal of 21021120 is 2112012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 25515 + ... + 26325.

Almost surely, 2^21021120 is an apocalyptic number.

21021120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21021120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37434012).

21021120 is an abundant number, since it is smaller than the sum of its proper divisors (53846904).

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

21021120 is an equidigital number, since it uses as much as digits as its factorization.

21021120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 840 (or 821 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21021120 is about 4584.8794967807. The cubic root of 21021120 is about 275.9848762980.

Adding to 21021120 its reverse (2112012), we get a palindrome (23133132).

The spelling of 21021120 in words is "twenty-one million, twenty-one thousand, one hundred twenty".