21986666 has 16 divisors (see below), whose sum is σ = 37062144. Its totient is φ = 9706224.

The previous prime is 21986639. The next prime is 21986683. The reversal of 21986666 is 66668912.

21986666 is a modest number, since divided by 6666 gives 2198 as remainder.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17786 + ... + 18981.

It is an arithmetic number, because the mean of its divisors is an integer number (2316384).

Almost surely, 2^21986666 is an apocalyptic number.

21986666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21986666 is a deficient number, since it is larger than the sum of its proper divisors (15075478).

21986666 is a wasteful number, since it uses less digits than its factorization.

21986666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36805.

The product of its digits is 186624, while the sum is 44.

The square root of 21986666 is about 4688.9941352064. The cubic root of 21986666 is about 280.1473119393.

The spelling of 21986666 in words is "twenty-one million, nine hundred eighty-six thousand, six hundred sixty-six".