21606123 has 32 divisors (see below), whose sum is σ = 36260352. Its totient is φ = 11209440.

The previous prime is 21606119. The next prime is 21606149. The reversal of 21606123 is 32160612.

It is a happy number.

It is not a de Polignac number, because 21606123 - 2² = 21606119 is a prime.

It is a super-2 number, since 2×21606123² = 933649102182258, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21606123.

It is not an unprimeable number, because it can be changed into a prime (21606023) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 27565 + ... + 28337.

It is an arithmetic number, because the mean of its divisors is an integer number (1133136).

Almost surely, 2^21606123 is an apocalyptic number.

21606123 is a deficient number, since it is larger than the sum of its proper divisors (14654229).

21606123 is an equidigital number, since it uses as much as digits as its factorization.

21606123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 816 (or 794 counting only the distinct ones).

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

The square root of 21606123 is about 4648.2386986901. The cubic root of 21606123 is about 278.5216427606.

Adding to 21606123 its reverse (32160612), we get a palindrome (53766735).

The spelling of 21606123 in words is "twenty-one million, six hundred six thousand, one hundred twenty-three".