21689623 has 4 divisors (see below), whose sum is σ = 21785400. Its totient is φ = 21593848.

The previous prime is 21689617. The next prime is 21689627. The reversal of 21689623 is 32698612.

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 21689623 - 2⁹ = 21689111 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 (21689627) 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, 47548 + ... + 48001.

It is an arithmetic number, because the mean of its divisors is an integer number (5446350).

Almost surely, 2^21689623 is an apocalyptic number.

21689623 is a deficient number, since it is larger than the sum of its proper divisors (95777).

21689623 is an equidigital number, since it uses as much as digits as its factorization.

21689623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95776.

The product of its digits is 31104, while the sum is 37.

The square root of 21689623 is about 4657.2119341941. The cubic root of 21689623 is about 278.8799773229.

The spelling of 21689623 in words is "twenty-one million, six hundred eighty-nine thousand, six hundred twenty-three".