21256973 has 4 divisors (see below), whose sum is σ = 21313440. Its totient is φ = 21200508.

The previous prime is 21256931. The next prime is 21256997. The reversal of 21256973 is 37965212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21256973 - 2⁶ = 21256909 is a prime.

It is a super-2 number, since 2×21256973² = 903717802245458, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256673) 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 3 ways as a sum of consecutive naturals, for example, 27665 + ... + 28422.

It is an arithmetic number, because the mean of its divisors is an integer number (5328360).

Almost surely, 2^21256973 is an apocalyptic number.

It is an amenable number.

21256973 is a deficient number, since it is larger than the sum of its proper divisors (56467).

21256973 is an equidigital number, since it uses as much as digits as its factorization.

21256973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56466.

The product of its digits is 22680, while the sum is 35.

The square root of 21256973 is about 4610.5284946522. The cubic root of 21256973 is about 277.0132060241.

The spelling of 21256973 in words is "twenty-one million, two hundred fifty-six thousand, nine hundred seventy-three".