21243331 has 2 divisors, whose sum is σ = 21243332. Its totient is φ = 21243330.

The previous prime is 21243307. The next prime is 21243347. The reversal of 21243331 is 13334212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243331 is a prime.

It is a super-2 number, since 2×21243331² = 902558223951122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21243299 and 21243308.

It is not a weakly prime, because it can be changed into another prime (21243361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621665 + 10621666.

It is an arithmetic number, because the mean of its divisors is an integer number (10621666).

Almost surely, 2^21243331 is an apocalyptic number.

21243331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243331 is an equidigital number, since it uses as much as digits as its factorization.

21243331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 19.

The square root of 21243331 is about 4609.0488172724. The cubic root of 21243331 is about 276.9539341347.

Adding to 21243331 its reverse (13334212), we get a palindrome (34577543).

The spelling of 21243331 in words is "twenty-one million, two hundred forty-three thousand, three hundred thirty-one".