21706816 has 28 divisors (see below), whose sum is σ = 45344080. Its totient is φ = 10281600.

The previous prime is 21706813. The next prime is 21706823. The reversal of 21706816 is 61860712.

It is not an unprimeable number, because it can be changed into a prime (21706813) 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, 7710 + ... + 10141.

Almost surely, 2^21706816 is an apocalyptic number.

It is an amenable number.

21706816 is an abundant number, since it is smaller than the sum of its proper divisors (23637264).

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

21706816 is a wasteful number, since it uses less digits than its factorization.

21706816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17882 (or 17872 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21706816 is about 4659.0574154007. The cubic root of 21706816 is about 278.9536456864.

It can be divided in two parts, 21706 and 816, that added together give a palindrome (22522).

The spelling of 21706816 in words is "twenty-one million, seven hundred six thousand, eight hundred sixteen".