21891400 has 48 divisors (see below), whose sum is σ = 53121600. Its totient is φ = 8374080.

The previous prime is 21891391. The next prime is 21891413. The reversal of 21891400 is 419812.

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 polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2221 + ... + 6979.

It is an arithmetic number, because the mean of its divisors is an integer number (1106700).

Almost surely, 2^21891400 is an apocalyptic number.

21891400 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 21891400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26560800).

21891400 is an abundant number, since it is smaller than the sum of its proper divisors (31230200).

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

21891400 is a wasteful number, since it uses less digits than its factorization.

21891400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4798 (or 4789 counting only the distinct ones).

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

The square root of 21891400 is about 4678.8246387314. The cubic root of 21891400 is about 279.7421094848.

The spelling of 21891400 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred".