21103872 has 36 divisors (see below), whose sum is σ = 56169120. Its totient is φ = 7034368.

The previous prime is 21103847. The next prime is 21103879. The reversal of 21103872 is 27830112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21103879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12972 + ... + 14507.

Almost surely, 2^21103872 is an apocalyptic number.

It is an amenable number.

21103872 is an abundant number, since it is smaller than the sum of its proper divisors (35065248).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21103872 is an equidigital number, since it uses as much as digits as its factorization.

21103872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27498 (or 27484 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21103872 is about 4593.8950793417. The cubic root of 21103872 is about 276.3465506100.

Adding to 21103872 its reverse (27830112), we get a palindrome (48933984).

The spelling of 21103872 in words is "twenty-one million, one hundred three thousand, eight hundred seventy-two".