21456591 has 8 divisors (see below), whose sum is σ = 30809520. Its totient is φ = 13204032.

The previous prime is 21456583. The next prime is 21456593. The reversal of 21456591 is 19565412.

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

It is not a de Polignac number, because 21456591 - 2³ = 21456583 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456593) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 275046 + ... + 275123.

It is an arithmetic number, because the mean of its divisors is an integer number (3851190).

Almost surely, 2^21456591 is an apocalyptic number.

21456591 is a deficient number, since it is larger than the sum of its proper divisors (9352929).

21456591 is a wasteful number, since it uses less digits than its factorization.

21456591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 550185.

The product of its digits is 10800, while the sum is 33.

The square root of 21456591 is about 4632.1259697897. The cubic root of 21456591 is about 277.8776224127.

The spelling of 21456591 in words is "twenty-one million, four hundred fifty-six thousand, five hundred ninety-one".