21504000 has 224 divisors, whose sum is σ = 81783936. Its totient is φ = 4915200.

The previous prime is 21503981. The next prime is 21504017. The reversal of 21504000 is 40512.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3071997 + ... + 3072003.

Almost surely, 2^21504000 is an apocalyptic number.

21504000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21504000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40891968).

21504000 is an abundant number, since it is smaller than the sum of its proper divisors (60279936).

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

21504000 is an frugal number, since it uses more digits than its factorization.

21504000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51 (or 17 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21504000 is about 4637.2405587806. The cubic root of 21504000 is about 278.0821315909.

Adding to 21504000 its reverse (40512), we get a palindrome (21544512).

The spelling of 21504000 in words is "twenty-one million, five hundred four thousand".