21004144 has 60 divisors (see below), whose sum is σ = 48118944. Its totient is φ = 8854272.

The previous prime is 21004117. The next prime is 21004153. The reversal of 21004144 is 44140012.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 57049 + ... + 57415.

Almost surely, 2^21004144 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 21004144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24059472).

21004144 is an abundant number, since it is smaller than the sum of its proper divisors (27114800).

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

21004144 is a wasteful number, since it uses less digits than its factorization.

21004144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462 (or 449 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21004144 is about 4583.0278201207. The cubic root of 21004144 is about 275.9105640347.

Adding to 21004144 its reverse (44140012), we get a palindrome (65144156).

The spelling of 21004144 in words is "twenty-one million, four thousand, one hundred forty-four".