21918080 has 64 divisors (see below), whose sum is σ = 54712800. Its totient is φ = 8380416.

The previous prime is 21918079. The next prime is 21918101. The reversal of 21918080 is 8081912.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13976 + ... + 15464.

Almost surely, 2^21918080 is an apocalyptic number.

21918080 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 21918080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27356400).

21918080 is an abundant number, since it is smaller than the sum of its proper divisors (32794720).

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

21918080 is a wasteful number, since it uses less digits than its factorization.

21918080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1531 (or 1519 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 21918080 is about 4681.6749139597. The cubic root of 21918080 is about 279.8557079679.

Adding to 21918080 its reverse (8081912), we get a palindrome (29999992).

The spelling of 21918080 in words is "twenty-one million, nine hundred eighteen thousand, eighty".