21387623 has 4 divisors (see below), whose sum is σ = 21577008. Its totient is φ = 21198240.

The previous prime is 21387617. The next prime is 21387629. The reversal of 21387623 is 32678312.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (21387617) and next prime (21387629).

It is a cyclic number.

It is not a de Polignac number, because 21387623 - 2¹⁴ = 21371239 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 21387623.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387629) 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 3 ways as a sum of consecutive naturals, for example, 94523 + ... + 94748.

It is an arithmetic number, because the mean of its divisors is an integer number (5394252).

Almost surely, 2^21387623 is an apocalyptic number.

21387623 is a deficient number, since it is larger than the sum of its proper divisors (189385).

21387623 is a wasteful number, since it uses less digits than its factorization.

21387623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189384.

The product of its digits is 12096, while the sum is 32.

The square root of 21387623 is about 4624.6754480720. The cubic root of 21387623 is about 277.5795751554.

The spelling of 21387623 in words is "twenty-one million, three hundred eighty-seven thousand, six hundred twenty-three".