21108423 has 16 divisors (see below), whose sum is σ = 32414976. Its totient is φ = 11968320.

The previous prime is 21108419. The next prime is 21108431. The reversal of 21108423 is 32480112.

It is not a de Polignac number, because 21108423 - 2² = 21108419 is a prime.

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 21108423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1086 + ... + 6587.

It is an arithmetic number, because the mean of its divisors is an integer number (2025936).

Almost surely, 2^21108423 is an apocalyptic number.

21108423 is a deficient number, since it is larger than the sum of its proper divisors (11306553).

21108423 is a wasteful number, since it uses less digits than its factorization.

21108423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7814.

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21108423 is about 4594.3903839356. The cubic root of 21108423 is about 276.3664136752.

Adding to 21108423 its reverse (32480112), we get a palindrome (53588535).

The spelling of 21108423 in words is "twenty-one million, one hundred eight thousand, four hundred twenty-three".