21601623 has 16 divisors (see below), whose sum is σ = 30698496. Its totient is φ = 13479840.

The previous prime is 21601603. The next prime is 21601627. The reversal of 21601623 is 32610612.

It is a happy number.

It is not a de Polignac number, because 21601623 - 2⁸ = 21601367 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21601623.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21601627) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 88 + ... + 6573.

It is an arithmetic number, because the mean of its divisors is an integer number (1918656).

Almost surely, 2^21601623 is an apocalyptic number.

21601623 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21601623 is a deficient number, since it is larger than the sum of its proper divisors (9096873).

21601623 is a wasteful number, since it uses less digits than its factorization.

21601623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6734.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21601623 is about 4647.7546191683. The cubic root of 21601623 is about 278.5023051186.

The spelling of 21601623 in words is "twenty-one million, six hundred one thousand, six hundred twenty-three".