21131233 has 4 divisors (see below), whose sum is σ = 21428928. Its totient is φ = 20833540.

The previous prime is 21131191. The next prime is 21131251. The reversal of 21131233 is 33213112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21131233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131293) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 148741 + ... + 148882.

It is an arithmetic number, because the mean of its divisors is an integer number (5357232).

Almost surely, 2^21131233 is an apocalyptic number.

It is an amenable number.

21131233 is a deficient number, since it is larger than the sum of its proper divisors (297695).

21131233 is an equidigital number, since it uses as much as digits as its factorization.

21131233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297694.

The product of its digits is 108, while the sum is 16.

The square root of 21131233 is about 4596.8720887142. The cubic root of 21131233 is about 276.4659260604.

Adding to 21131233 its reverse (33213112), we get a palindrome (54344345).

The spelling of 21131233 in words is "twenty-one million, one hundred thirty-one thousand, two hundred thirty-three".