21668018 has 16 divisors (see below), whose sum is σ = 34379520. Its totient is φ = 10213776.

The previous prime is 21668011. The next prime is 21668033. The reversal of 21668018 is 81086612.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21668011) 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, 7196 + ... + 9752.

It is an arithmetic number, because the mean of its divisors is an integer number (2148720).

Almost surely, 2^21668018 is an apocalyptic number.

21668018 is a deficient number, since it is larger than the sum of its proper divisors (12711502).

21668018 is a wasteful number, since it uses less digits than its factorization.

21668018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2801.

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

The square root of 21668018 is about 4654.8918354780. The cubic root of 21668018 is about 278.7873492555.

The spelling of 21668018 in words is "twenty-one million, six hundred sixty-eight thousand, eighteen".