21708216 has 32 divisors (see below), whose sum is σ = 60301200. Its totient is φ = 7236000.

The previous prime is 21708209. The next prime is 21708221. The reversal of 21708216 is 61280712.

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 21708216.

It is a congruent 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, 50035 + ... + 50466.

Almost surely, 2^21708216 is an apocalyptic number.

It is an amenable number.

21708216 is an abundant number, since it is smaller than the sum of its proper divisors (38592984).

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

21708216 is a wasteful number, since it uses less digits than its factorization.

21708216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100516 (or 100506 counting only the distinct ones).

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

The square root of 21708216 is about 4659.2076579607. The cubic root of 21708216 is about 278.9596426769.

Adding to 21708216 its reverse (61280712), we get a palindrome (82988928).

The spelling of 21708216 in words is "twenty-one million, seven hundred eight thousand, two hundred sixteen".