21680166 has 8 divisors (see below), whose sum is σ = 43360344. Its totient is φ = 7226720.

The previous prime is 21680149. The next prime is 21680167. The reversal of 21680166 is 66108612.

It is a sphenic number, since it is the product of 3 distinct primes.

21680166 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680167) 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, 1806675 + ... + 1806686.

It is an arithmetic number, because the mean of its divisors is an integer number (5420043).

Almost surely, 2^21680166 is an apocalyptic number.

21680166 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21680166 is a wasteful number, since it uses less digits than its factorization.

21680166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3613366.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21680166 is about 4656.1965164714. The cubic root of 21680166 is about 278.8394394837.

Adding to 21680166 its reverse (66108612), we get a palindrome (87788778).

The spelling of 21680166 in words is "twenty-one million, six hundred eighty thousand, one hundred sixty-six".