21121020 has 48 divisors (see below), whose sum is σ = 65711520. Its totient is φ = 5632128.

The previous prime is 21121003. The next prime is 21121033. The reversal of 21121020 is 2012112.

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

It is a junction number, because it is equal to n+sod(n) for n = 21120993 and 21121011.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19017 + ... + 20096.

It is an arithmetic number, because the mean of its divisors is an integer number (1368990).

Almost surely, 2^21121020 is an apocalyptic number.

21121020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121020 is an abundant number, since it is smaller than the sum of its proper divisors (44590500).

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

21121020 is a wasteful number, since it uses less digits than its factorization.

21121020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39131 (or 39123 counting only the distinct ones).

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

The square root of 21121020 is about 4595.7610903962. The cubic root of 21121020 is about 276.4213790226.

Adding to 21121020 its reverse (2012112), we get a palindrome (23133132).

The spelling of 21121020 in words is "twenty-one million, one hundred twenty-one thousand, twenty".