21328400 has 60 divisors (see below), whose sum is σ = 52032384. Its totient is φ = 8400000.

The previous prime is 21328399. The next prime is 21328409. The reversal of 21328400 is 482312.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (21328409) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28025 + ... + 28775.

Almost surely, 2^21328400 is an apocalyptic number.

21328400 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 21328400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26016192).

21328400 is an abundant number, since it is smaller than the sum of its proper divisors (30703984).

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

21328400 is a wasteful number, since it uses less digits than its factorization.

21328400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 840 (or 829 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21328400 is about 4618.2680736397. The cubic root of 21328400 is about 277.3231294528.

The spelling of 21328400 in words is "twenty-one million, three hundred twenty-eight thousand, four hundred".