21818880 has 120 divisors (see below), whose sum is σ = 75644712. Its totient is φ = 5812224.

The previous prime is 21818873. The next prime is 21818893. The reversal of 21818880 is 8881812.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (120).

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

It is a congruent number.

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, 22567 + ... + 23513.

Almost surely, 2^21818880 is an apocalyptic number.

21818880 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 21818880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37822356).

21818880 is an abundant number, since it is smaller than the sum of its proper divisors (53825832).

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

21818880 is an equidigital number, since it uses as much as digits as its factorization.

21818880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 976 (or 957 counting only the distinct ones).

The product of its (nonzero) digits is 8192, while the sum is 36.

The square root of 21818880 is about 4671.0684002699. The cubic root of 21818880 is about 279.4328656619.

The spelling of 21818880 in words is "twenty-one million, eight hundred eighteen thousand, eight hundred eighty".