21585623 has 4 divisors (see below), whose sum is σ = 21637560. Its totient is φ = 21533688.

The previous prime is 21585617. The next prime is 21585649. The reversal of 21585623 is 32658512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21585623 - 2⁶ = 21585559 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21585623.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21585673) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25340 + ... + 26177.

It is an arithmetic number, because the mean of its divisors is an integer number (5409390).

Almost surely, 2^21585623 is an apocalyptic number.

21585623 is a deficient number, since it is larger than the sum of its proper divisors (51937).

21585623 is an equidigital number, since it uses as much as digits as its factorization.

21585623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51936.

The product of its digits is 14400, while the sum is 32.

The square root of 21585623 is about 4646.0330390560. The cubic root of 21585623 is about 278.4335273003.

The spelling of 21585623 in words is "twenty-one million, five hundred eighty-five thousand, six hundred twenty-three".