21285623 has 8 divisors (see below), whose sum is σ = 22730880. Its totient is φ = 19887840.

The previous prime is 21285611. The next prime is 21285631. The reversal of 21285623 is 32658212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21285623 - 2⁸ = 21285367 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21285673) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10940 + ... + 12737.

It is an arithmetic number, because the mean of its divisors is an integer number (2841360).

Almost surely, 2^21285623 is an apocalyptic number.

21285623 is a deficient number, since it is larger than the sum of its proper divisors (1445257).

21285623 is a wasteful number, since it uses less digits than its factorization.

21285623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23737.

The product of its digits is 5760, while the sum is 29.

The square root of 21285623 is about 4613.6344675321. The cubic root of 21285623 is about 277.1376023099.

The spelling of 21285623 in words is "twenty-one million, two hundred eighty-five thousand, six hundred twenty-three".