21218880 has 168 divisors, whose sum is σ = 72639936. Its totient is φ = 5237760.

The previous prime is 21218863. The next prime is 21218887. The reversal of 21218880 is 8881212.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (21218887) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 684465 + ... + 684495.

Almost surely, 2^21218880 is an apocalyptic number.

21218880 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 21218880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36319968).

21218880 is an abundant number, since it is smaller than the sum of its proper divisors (51421056).

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

21218880 is a wasteful number, since it uses less digits than its factorization.

21218880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105 (or 64 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 30.

The square root of 21218880 is about 4606.3955540097. The cubic root of 21218880 is about 276.8476356700.

The spelling of 21218880 in words is "twenty-one million, two hundred eighteen thousand, eight hundred eighty".