21680016 has 20 divisors (see below), whose sum is σ = 56006832. Its totient is φ = 7226656.

The previous prime is 21680003. The next prime is 21680017. The reversal of 21680016 is 61008612.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is not an unprimeable number, because it can be changed into a prime (21680017) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 225786 + ... + 225881.

Almost surely, 2^21680016 is an apocalyptic number.

It is an amenable number.

21680016 is an abundant number, since it is smaller than the sum of its proper divisors (34326816).

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

21680016 is a wasteful number, since it uses less digits than its factorization.

21680016 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 451678 (or 451672 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 21680016 is about 4656.1804088759. The cubic root of 21680016 is about 278.8387964072.

Adding to 21680016 its reverse (61008612), we get a palindrome (82688628).

The spelling of 21680016 in words is "twenty-one million, six hundred eighty thousand, sixteen".