21707680 has 48 divisors (see below), whose sum is σ = 51607584. Its totient is φ = 8628480.

The previous prime is 21707603. The next prime is 21707701. The reversal of 21707680 is 8670712.

21707680 = T₃₄₄ + T₃₄₅ + ... + T₅₅₄.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33439 + ... + 34081.

It is an arithmetic number, because the mean of its divisors is an integer number (1075158).

Almost surely, 2^21707680 is an apocalyptic number.

21707680 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 21707680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25803792).

21707680 is an abundant number, since it is smaller than the sum of its proper divisors (29899904).

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

21707680 is a wasteful number, since it uses less digits than its factorization.

21707680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 869 (or 861 counting only the distinct ones).

The product of its (nonzero) digits is 4704, while the sum is 31.

The square root of 21707680 is about 4659.1501370958. The cubic root of 21707680 is about 278.9573467167.

It can be divided in two parts, 217076 and 80, that added together give a square (217156 = 466²).

The spelling of 21707680 in words is "twenty-one million, seven hundred seven thousand, six hundred eighty".