21321021 has 12 divisors (see below), whose sum is σ = 30004512. Its totient is φ = 13465224.

The previous prime is 21321019. The next prime is 21321031. The reversal of 21321021 is 12012312.

It is not a de Polignac number, because 21321021 - 2¹ = 21321019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21320988 and 21321006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321031) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 8761 + ... + 10926.

It is an arithmetic number, because the mean of its divisors is an integer number (2500376).

Almost surely, 2^21321021 is an apocalyptic number.

It is an amenable number.

21321021 is a deficient number, since it is larger than the sum of its proper divisors (8683491).

21321021 is a wasteful number, since it uses less digits than its factorization.

21321021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19728 (or 19709 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21321021 is about 4617.4691119703. The cubic root of 21321021 is about 277.2911438778.

Adding to 21321021 its reverse (12012312), we get a palindrome (33333333).

The spelling of 21321021 in words is "twenty-one million, three hundred twenty-one thousand, twenty-one".