21256679 has 2 divisors, whose sum is σ = 21256680. Its totient is φ = 21256678.

The previous prime is 21256673. The next prime is 21256691. The reversal of 21256679 is 97665212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21256679 - 2¹⁶ = 21191143 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21256673) 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, 10628339 + 10628340.

It is an arithmetic number, because the mean of its divisors is an integer number (10628340).

Almost surely, 2^21256679 is an apocalyptic number.

21256679 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256679 is an equidigital number, since it uses as much as digits as its factorization.

21256679 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 38.

The square root of 21256679 is about 4610.4966109954. The cubic root of 21256679 is about 277.0119289176.

The spelling of 21256679 in words is "twenty-one million, two hundred fifty-six thousand, six hundred seventy-nine".