21708680 has 128 divisors (see below), whose sum is σ = 59996160. Its totient is φ = 6912000.

The previous prime is 21708671. The next prime is 21708703. The reversal of 21708680 is 8680712.

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 31 ways as a sum of consecutive naturals, for example, 355850 + ... + 355910.

It is an arithmetic number, because the mean of its divisors is an integer number (468720).

Almost surely, 2^21708680 is an apocalyptic number.

21708680 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 21708680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29998080).

21708680 is an abundant number, since it is smaller than the sum of its proper divisors (38287480).

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

21708680 is a wasteful number, since it uses less digits than its factorization.

21708680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151 (or 147 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 32.

The square root of 21708680 is about 4659.2574515689. The cubic root of 21708680 is about 278.9616301940.

It can be divided in two parts, 2170 and 8680, that multiplied together give a square (18835600 = 4340²).

The spelling of 21708680 in words is "twenty-one million, seven hundred eight thousand, six hundred eighty".