21680816 has 40 divisors (see below), whose sum is σ = 44019504. Its totient is φ = 10333440.

The previous prime is 21680807. The next prime is 21680819. The reversal of 21680816 is 61808612.

It is not an unprimeable number, because it can be changed into a prime (21680819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31031 + ... + 31721.

Almost surely, 2^21680816 is an apocalyptic number.

It is an amenable number.

21680816 is an abundant number, since it is smaller than the sum of its proper divisors (22338688).

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

21680816 is a wasteful number, since it uses less digits than its factorization.

21680816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 789 (or 783 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21680816 is about 4656.2663154077. The cubic root of 21680816 is about 278.8422261140.

The spelling of 21680816 in words is "twenty-one million, six hundred eighty thousand, eight hundred sixteen".