21256823 has 8 divisors (see below), whose sum is σ = 24399648. Its totient is φ = 18140544.

The previous prime is 21256813. The next prime is 21256841. The reversal of 21256823 is 32865212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21256823 - 2⁸ = 21256567 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256813) 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 in 7 ways as a sum of consecutive naturals, for example, 4886 + ... + 8147.

It is an arithmetic number, because the mean of its divisors is an integer number (3049956).

Almost surely, 2^21256823 is an apocalyptic number.

21256823 is a deficient number, since it is larger than the sum of its proper divisors (3142825).

21256823 is a wasteful number, since it uses less digits than its factorization.

21256823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13273.

The product of its digits is 5760, while the sum is 29.

The square root of 21256823 is about 4610.5122275079. The cubic root of 21256823 is about 277.0125544406.

The spelling of 21256823 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred twenty-three".