21256775 has 6 divisors (see below), whose sum is σ = 26358432. Its totient is φ = 17005400.

The previous prime is 21256771. The next prime is 21256777. The reversal of 21256775 is 57765212.

It is a happy number.

It is not a de Polignac number, because 21256775 - 2² = 21256771 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 425111 + ... + 425160.

It is an arithmetic number, because the mean of its divisors is an integer number (4393072).

Almost surely, 2^21256775 is an apocalyptic number.

21256775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21256775 is a deficient number, since it is larger than the sum of its proper divisors (5101657).

21256775 is an equidigital number, since it uses as much as digits as its factorization.

21256775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 850281 (or 850276 counting only the distinct ones).

The product of its digits is 29400, while the sum is 35.

The square root of 21256775 is about 4610.5070220096. The cubic root of 21256775 is about 277.0123459332.

The spelling of 21256775 in words is "twenty-one million, two hundred fifty-six thousand, seven hundred seventy-five".