21730680 has 160 divisors (see below), whose sum is σ = 77101200. Its totient is φ = 5474304.

The previous prime is 21730663. The next prime is 21730693. The reversal of 21730680 is 8603712.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 61384 + ... + 61736.

Almost surely, 2^21730680 is an apocalyptic number.

21730680 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 21730680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38550600).

21730680 is an abundant number, since it is smaller than the sum of its proper divisors (55370520).

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

21730680 is a wasteful number, since it uses less digits than its factorization.

21730680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 395 (or 382 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21730680 is about 4661.6177449465. The cubic root of 21730680 is about 279.0558334322.

The spelling of 21730680 in words is "twenty-one million, seven hundred thirty thousand, six hundred eighty".