21493231 has 2 divisors, whose sum is σ = 21493232. Its totient is φ = 21493230.

The previous prime is 21493229. The next prime is 21493243. The reversal of 21493231 is 13239412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21493231 - 2¹ = 21493229 is a prime.

It is a super-2 number, since 2×21493231² = 923917957638722, which contains 22 as substring.

Together with 21493229, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21493196 and 21493205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21493331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746615 + 10746616.

It is an arithmetic number, because the mean of its divisors is an integer number (10746616).

Almost surely, 2^21493231 is an apocalyptic number.

21493231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493231 is an equidigital number, since it uses as much as digits as its factorization.

21493231 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 25.

The square root of 21493231 is about 4636.0792702455. The cubic root of 21493231 is about 278.0357035385.

The spelling of 21493231 in words is "twenty-one million, four hundred ninety-three thousand, two hundred thirty-one".