21066666 has 16 divisors (see below), whose sum is σ = 43965504. Its totient is φ = 6716864.

The previous prime is 21066641. The next prime is 21066677. The reversal of 21066666 is 66666012.

21066666 is a modest number, since divided by 6666 gives 2106 as remainder.

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, 76191 + ... + 76466.

It is an arithmetic number, because the mean of its divisors is an integer number (2747844).

Almost surely, 2^21066666 is an apocalyptic number.

21066666 is an abundant number, since it is smaller than the sum of its proper divisors (22898838).

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

21066666 is a wasteful number, since it uses less digits than its factorization.

21066666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152685.

The product of its (nonzero) digits is 15552, while the sum is 33.

The square root of 21066666 is about 4589.8437881915. The cubic root of 21066666 is about 276.1840559754.

The spelling of 21066666 in words is "twenty-one million, sixty-six thousand, six hundred sixty-six".