21918480 has 80 divisors (see below), whose sum is σ = 68400384. Its totient is φ = 5806080.

The previous prime is 21918473. The next prime is 21918509. The reversal of 21918480 is 8481912.

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

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 15 ways as a sum of consecutive naturals, for example, 64872 + ... + 65208.

Almost surely, 2^21918480 is an apocalyptic number.

21918480 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 21918480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34200192).

21918480 is an abundant number, since it is smaller than the sum of its proper divisors (46481904).

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

21918480 is a wasteful number, since it uses less digits than its factorization.

21918480 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 624 (or 618 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 33.

The square root of 21918480 is about 4681.7176335187. The cubic root of 21918480 is about 279.8574103920.

The spelling of 21918480 in words is "twenty-one million, nine hundred eighteen thousand, four hundred eighty".