21918400 has 168 divisors, whose sum is σ = 65511680. Its totient is φ = 7050240.

The previous prime is 21918397. The next prime is 21918427. The reversal of 21918400 is 481912.

It is a happy number.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 212749 + ... + 212851.

Almost surely, 2^21918400 is an apocalyptic number.

21918400 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 21918400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32755840).

21918400 is an abundant number, since it is smaller than the sum of its proper divisors (43593280).

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

21918400 is a wasteful number, since it uses less digits than its factorization.

21918400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151 (or 136 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21918400 is about 4681.7090896381. The cubic root of 21918400 is about 279.8570699088.

The spelling of 21918400 in words is "twenty-one million, nine hundred eighteen thousand, four hundred".