21321231 has 8 divisors (see below), whose sum is σ = 28788480. Its totient is φ = 14034072.

The previous prime is 21321217. The next prime is 21321263. The reversal of 21321231 is 13212312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21321231 - 2⁵ = 21321199 is a prime.

It is a super-2 number, since 2×21321231² = 909189782710722, 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 21321231.

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 polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44745 + ... + 45218.

It is an arithmetic number, because the mean of its divisors is an integer number (3598560).

Almost surely, 2^21321231 is an apocalyptic number.

21321231 is a deficient number, since it is larger than the sum of its proper divisors (7467249).

21321231 is an equidigital number, since it uses as much as digits as its factorization.

21321231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90045.

The product of its digits is 72, while the sum is 15.

The square root of 21321231 is about 4617.4918516441. The cubic root of 21321231 is about 277.2920542618.

Adding to 21321231 its reverse (13212312), we get a palindrome (34533543).

It can be divided in two parts, 2 and 1321231, that multiplied together give a palindrome (2642462).

The spelling of 21321231 in words is "twenty-one million, three hundred twenty-one thousand, two hundred thirty-one".