21894840 has 256 divisors, whose sum is σ = 84672000. Its totient is φ = 4976640.

The previous prime is 21894839. The next prime is 21894871. The reversal of 21894840 is 4849812.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21894795 and 21894804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 225672 + ... + 225768.

It is an arithmetic number, because the mean of its divisors is an integer number (330750).

Almost surely, 2^21894840 is an apocalyptic number.

21894840 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 21894840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42336000).

21894840 is an abundant number, since it is smaller than the sum of its proper divisors (62777160).

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

21894840 is a wasteful number, since it uses less digits than its factorization.

21894840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147 (or 137 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 21894840 is about 4679.1922379830. The cubic root of 21894840 is about 279.7567615469.

The spelling of 21894840 in words is "twenty-one million, eight hundred ninety-four thousand, eight hundred forty".