21258431 has 2 divisors, whose sum is σ = 21258432. Its totient is φ = 21258430.

The previous prime is 21258407. The next prime is 21258437. The reversal of 21258431 is 13485212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21258431 - 2¹⁰ = 21257407 is a prime.

It is a super-4 number, since 4×21258431⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21258431.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21258437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10629215 + 10629216.

It is an arithmetic number, because the mean of its divisors is an integer number (10629216).

Almost surely, 2^21258431 is an apocalyptic number.

21258431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21258431 is an equidigital number, since it uses as much as digits as its factorization.

21258431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1920, while the sum is 26.

The square root of 21258431 is about 4610.6866083047. The cubic root of 21258431 is about 277.0195392560.

The spelling of 21258431 in words is "twenty-one million, two hundred fifty-eight thousand, four hundred thirty-one".