21856400 has 60 divisors (see below), whose sum is σ = 53127924. Its totient is φ = 8640000.

The previous prime is 21856399. The next prime is 21856409. The reversal of 21856400 is 465812.

It can be written as a sum of positive squares in 6 ways, for example, as 215296 + 21641104 = 464^2 + 4652^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21856400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21856409) 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, 40130 + ... + 40670.

Almost surely, 2^21856400 is an apocalyptic number.

21856400 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 21856400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26563962).

21856400 is an abundant number, since it is smaller than the sum of its proper divisors (31271524).

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

21856400 is a wasteful number, since it uses less digits than its factorization.

21856400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660 (or 649 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21856400 is about 4675.0828869657. The cubic root of 21856400 is about 279.5929459410.

The spelling of 21856400 in words is "twenty-one million, eight hundred fifty-six thousand, four hundred".