21702816 has 72 divisors (see below), whose sum is σ = 64026144. Its totient is φ = 7231680.

The previous prime is 21702809. The next prime is 21702833. The reversal of 21702816 is 61820712.

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a self number, because there is not a number n which added to its sum of digits gives 21702816.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6381 + ... + 9171.

It is an arithmetic number, because the mean of its divisors is an integer number (889252).

Almost surely, 2^21702816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21702816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32013072).

21702816 is an abundant number, since it is smaller than the sum of its proper divisors (42323328).

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

21702816 is an equidigital number, since it uses as much as digits as its factorization.

21702816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2816 (or 2796 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21702816 is about 4658.6281242443. The cubic root of 21702816 is about 278.9365100068.

The spelling of 21702816 in words is "twenty-one million, seven hundred two thousand, eight hundred sixteen".