21257843 has 2 divisors, whose sum is σ = 21257844. Its totient is φ = 21257842.

The previous prime is 21257809. The next prime is 21257849. The reversal of 21257843 is 34875212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21257843 - 2⁶ = 21257779 is a prime.

It is not a weakly prime, because it can be changed into another prime (21257849) 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, 10628921 + 10628922.

It is an arithmetic number, because the mean of its divisors is an integer number (10628922).

Almost surely, 2^21257843 is an apocalyptic number.

21257843 is a deficient number, since it is larger than the sum of its proper divisors (1).

21257843 is an equidigital number, since it uses as much as digits as its factorization.

21257843 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13440, while the sum is 32.

The square root of 21257843 is about 4610.6228429573. The cubic root of 21257843 is about 277.0169851480.

The spelling of 21257843 in words is "twenty-one million, two hundred fifty-seven thousand, eight hundred forty-three".