21375623 has 4 divisors (see below), whose sum is σ = 21413760. Its totient is φ = 21337488.

The previous prime is 21375617. The next prime is 21375631. The reversal of 21375623 is 32657312.

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 21375623 - 2¹⁰ = 21374599 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21375023) 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, 18215 + ... + 19352.

It is an arithmetic number, because the mean of its divisors is an integer number (5353440).

Almost surely, 2^21375623 is an apocalyptic number.

21375623 is a deficient number, since it is larger than the sum of its proper divisors (38137).

21375623 is an equidigital number, since it uses as much as digits as its factorization.

21375623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38136.

The product of its digits is 7560, while the sum is 29.

The square root of 21375623 is about 4623.3778776994. The cubic root of 21375623 is about 277.5276513852.

The spelling of 21375623 in words is "twenty-one million, three hundred seventy-five thousand, six hundred twenty-three".