21864400 has 60 divisors (see below), whose sum is σ = 53692992. Its totient is φ = 8552320.

The previous prime is 21864389. The next prime is 21864407. The reversal of 21864400 is 446812.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864407) 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, 18219 + ... + 19381.

Almost surely, 2^21864400 is an apocalyptic number.

21864400 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 21864400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26846496).

21864400 is an abundant number, since it is smaller than the sum of its proper divisors (31828592).

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

21864400 is a wasteful number, since it uses less digits than its factorization.

21864400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1228 (or 1217 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 21864400 is about 4675.9384084909. The cubic root of 21864400 is about 279.6270544969.

The spelling of 21864400 in words is "twenty-one million, eight hundred sixty-four thousand, four hundred".