21696623 has 4 divisors (see below), whose sum is σ = 23365608. Its totient is φ = 20027640.

The previous prime is 21696617. The next prime is 21696629. The reversal of 21696623 is 32669612.

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 (21696617) and next prime (21696629).

It is a cyclic number.

It is not a de Polignac number, because 21696623 - 2¹⁰ = 21695599 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 (21696629) 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, 834473 + ... + 834498.

It is an arithmetic number, because the mean of its divisors is an integer number (5841402).

Almost surely, 2^21696623 is an apocalyptic number.

21696623 is a deficient number, since it is larger than the sum of its proper divisors (1668985).

21696623 is a wasteful number, since it uses less digits than its factorization.

21696623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1668984.

The product of its digits is 23328, while the sum is 35.

The square root of 21696623 is about 4657.9633961636. The cubic root of 21696623 is about 278.9099755371.

The spelling of 21696623 in words is "twenty-one million, six hundred ninety-six thousand, six hundred twenty-three".