21718580 has 48 divisors (see below), whose sum is σ = 49655424. Its totient is φ = 7931520.

The previous prime is 21718553. The next prime is 21718583. The reversal of 21718580 is 8581712.

It is a happy number.

It is a zygodrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718583) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26375 + ... + 27185.

It is an arithmetic number, because the mean of its divisors is an integer number (1034488).

Almost surely, 2^21718580 is an apocalyptic number.

21718580 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 21718580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24827712).

21718580 is an abundant number, since it is smaller than the sum of its proper divisors (27936844).

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

21718580 is a wasteful number, since it uses less digits than its factorization.

21718580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 936 (or 934 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21718580 is about 4660.3197315206. The cubic root of 21718580 is about 279.0040295235.

The spelling of 21718580 in words is "twenty-one million, seven hundred eighteen thousand, five hundred eighty".