21680418 has 16 divisors (see below), whose sum is σ = 43972416. Its totient is φ = 7124880.

The previous prime is 21680413. The next prime is 21680419. The reversal of 21680418 is 81408612.

It is not an unprimeable number, because it can be changed into a prime (21680413) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25021 + ... + 25872.

It is an arithmetic number, because the mean of its divisors is an integer number (2748276).

Almost surely, 2^21680418 is an apocalyptic number.

21680418 is an abundant number, since it is smaller than the sum of its proper divisors (22291998).

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

21680418 is a wasteful number, since it uses less digits than its factorization.

21680418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50969.

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21680418 is about 4656.2235771062. The cubic root of 21680418 is about 278.8405198454.

The spelling of 21680418 in words is "twenty-one million, six hundred eighty thousand, four hundred eighteen".