21100144 has 40 divisors (see below), whose sum is σ = 44774912. Its totient is φ = 9573120.

The previous prime is 21100141. The next prime is 21100159. The reversal of 21100144 is 44100112.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100141) 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, 11857 + ... + 13519.

Almost surely, 2^21100144 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21100144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22387456).

21100144 is an abundant number, since it is smaller than the sum of its proper divisors (23674768).

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

21100144 is a wasteful number, since it uses less digits than its factorization.

21100144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1745 (or 1739 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21100144 is about 4593.4893055280. The cubic root of 21100144 is about 276.3302774412.

Subtracting from 21100144 its product of nonzero digits (32), we obtain a palindrome (21100112).

Adding to 21100144 its reverse (44100112), we get a palindrome (65200256).

The spelling of 21100144 in words is "twenty-one million, one hundred thousand, one hundred forty-four".