21021231 has 64 divisors (see below), whose sum is σ = 38071296. Its totient is φ = 9984000.

The previous prime is 21021229. The next prime is 21021251. The reversal of 21021231 is 13212012.

It is not a de Polignac number, because 21021231 - 2¹ = 21021229 is a prime.

It is a super-2 number, since 2×21021231² = 883784305510722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021251) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 208081 + ... + 208181.

It is an arithmetic number, because the mean of its divisors is an integer number (594864).

Almost surely, 2^21021231 is an apocalyptic number.

21021231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21021231 is a deficient number, since it is larger than the sum of its proper divisors (17050065).

21021231 is a wasteful number, since it uses less digits than its factorization.

21021231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192.

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

The square root of 21021231 is about 4584.8916017721. The cubic root of 21021231 is about 275.9853620676.

Adding to 21021231 its reverse (13212012), we get a palindrome (34233243).

It can be divided in two parts, 2102 and 1231, that added together give a palindrome (3333).

The spelling of 21021231 in words is "twenty-one million, twenty-one thousand, two hundred thirty-one".