21233831 has 4 divisors (see below), whose sum is σ = 21314832. Its totient is φ = 21152832.

The previous prime is 21233827. The next prime is 21233843. The reversal of 21233831 is 13833212.

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 21233831 - 2² = 21233827 is a prime.

It is a super-2 number, since 2×21233831² = 901751157873122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21233797 and 21233806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21233851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40106 + ... + 40631.

It is an arithmetic number, because the mean of its divisors is an integer number (5328708).

Almost surely, 2^21233831 is an apocalyptic number.

21233831 is a deficient number, since it is larger than the sum of its proper divisors (81001).

21233831 is an equidigital number, since it uses as much as digits as its factorization.

21233831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81000.

The product of its digits is 864, while the sum is 23.

The square root of 21233831 is about 4608.0181206241. The cubic root of 21233831 is about 276.9126434558.

It can be divided in two parts, 212 and 33831, that added together give a palindrome (34043).

The spelling of 21233831 in words is "twenty-one million, two hundred thirty-three thousand, eight hundred thirty-one".