21812231 has 4 divisors (see below), whose sum is σ = 24928272. Its totient is φ = 18696192.

The previous prime is 21812221. The next prime is 21812237. The reversal of 21812231 is 13221812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21812231 - 2¹⁴ = 21795847 is a prime.

It is a super-2 number, since 2×21812231² = 951546842394722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21812237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1558010 + ... + 1558023.

It is an arithmetic number, because the mean of its divisors is an integer number (6232068).

Almost surely, 2^21812231 is an apocalyptic number.

21812231 is a deficient number, since it is larger than the sum of its proper divisors (3116041).

21812231 is an equidigital number, since it uses as much as digits as its factorization.

21812231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3116040.

The product of its digits is 192, while the sum is 20.

The square root of 21812231 is about 4670.3566244988. The cubic root of 21812231 is about 279.4044783526.

The spelling of 21812231 in words is "twenty-one million, eight hundred twelve thousand, two hundred thirty-one".