21231231 has 32 divisors (see below), whose sum is σ = 34145280. Its totient is φ = 11472384.

The previous prime is 21231173. The next prime is 21231241. The reversal of 21231231 is 13213212.

It is not a de Polignac number, because 21231231 - 2⁹ = 21230719 is a prime.

It is a super-2 number, since 2×21231231² = 901530339550722, 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 21231231.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 54385 + ... + 54773.

It is an arithmetic number, because the mean of its divisors is an integer number (1067040).

Almost surely, 2^21231231 is an apocalyptic number.

21231231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21231231 is a deficient number, since it is larger than the sum of its proper divisors (12914049).

21231231 is a wasteful number, since it uses less digits than its factorization.

21231231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 535.

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

The square root of 21231231 is about 4607.7359950414. The cubic root of 21231231 is about 276.9013407025.

Adding to 21231231 its reverse (13213212), we get a palindrome (34444443).

The spelling of 21231231 in words is "twenty-one million, two hundred thirty-one thousand, two hundred thirty-one".