21121231 has 2 divisors, whose sum is σ = 21121232. Its totient is φ = 21121230.

The previous prime is 21121223. The next prime is 21121237. The reversal of 21121231 is 13212112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21121231 - 2³ = 21121223 is a prime.

It is a super-2 number, since 2×21121231² = 892212797910722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21121237) 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 as a sum of consecutive naturals, namely, 10560615 + 10560616.

It is an arithmetic number, because the mean of its divisors is an integer number (10560616).

Almost surely, 2^21121231 is an apocalyptic number.

21121231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121231 is an equidigital number, since it uses as much as digits as its factorization.

21121231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24, while the sum is 13.

The square root of 21121231 is about 4595.7840462755. The cubic root of 21121231 is about 276.4222995071.

Adding to 21121231 its reverse (13212112), we get a palindrome (34333343).

The spelling of 21121231 in words is "twenty-one million, one hundred twenty-one thousand, two hundred thirty-one".