21256403 has 8 divisors (see below), whose sum is σ = 24352608. Its totient is φ = 18175104.

The previous prime is 21256399. The next prime is 21256447. The reversal of 21256403 is 30465212.

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 21256403 - 2² = 21256399 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21256303) 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 7 ways as a sum of consecutive naturals, for example, 476 + ... + 6537.

It is an arithmetic number, because the mean of its divisors is an integer number (3044076).

Almost surely, 2^21256403 is an apocalyptic number.

21256403 is a deficient number, since it is larger than the sum of its proper divisors (3096205).

21256403 is an equidigital number, since it uses as much as digits as its factorization.

21256403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7453.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21256403 is about 4610.4666791985. The cubic root of 21256403 is about 277.0107299905.

The spelling of 21256403 in words is "twenty-one million, two hundred fifty-six thousand, four hundred three".