21297431 has 2 divisors, whose sum is σ = 21297432. Its totient is φ = 21297430.

The previous prime is 21297383. The next prime is 21297457. The reversal of 21297431 is 13479212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21297431 - 2¹⁴ = 21281047 is a prime.

It is a super-3 number, since 3×21297431³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21297394 and 21297403.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21297131) 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 as a sum of consecutive naturals, namely, 10648715 + 10648716.

It is an arithmetic number, because the mean of its divisors is an integer number (10648716).

Almost surely, 2^21297431 is an apocalyptic number.

21297431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21297431 is an equidigital number, since it uses as much as digits as its factorization.

21297431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 29.

The square root of 21297431 is about 4614.9139753629. The cubic root of 21297431 is about 277.1888393331.

The spelling of 21297431 in words is "twenty-one million, two hundred ninety-seven thousand, four hundred thirty-one".