21718900 has 144 divisors (see below), whose sum is σ = 59996160. Its totient is φ = 6652800.

The previous prime is 21718897. The next prime is 21718943. The reversal of 21718900 is 981712.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 305865 + ... + 305935.

It is an arithmetic number, because the mean of its divisors is an integer number (416640).

Almost surely, 2^21718900 is an apocalyptic number.

21718900 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 21718900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29998080).

21718900 is an abundant number, since it is smaller than the sum of its proper divisors (38277260).

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

21718900 is a wasteful number, since it uses less digits than its factorization.

21718900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134 (or 127 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21718900 is about 4660.3540638024. The cubic root of 21718900 is about 279.0053997919.

The spelling of 21718900 in words is "twenty-one million, seven hundred eighteen thousand, nine hundred".