21415666 has 16 divisors (see below), whose sum is σ = 32650200. Its totient is φ = 10533888.

The previous prime is 21415661. The next prime is 21415721. The reversal of 21415666 is 66651412.

It can be written as a sum of positive squares in 4 ways, for example, as 20025625 + 1390041 = 4475^2 + 1179^2 .

It is not an unprimeable number, because it can be changed into a prime (21415661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41820 + ... + 42328.

Almost surely, 2^21415666 is an apocalyptic number.

21415666 is a deficient number, since it is larger than the sum of its proper divisors (11234534).

21415666 is a wasteful number, since it uses less digits than its factorization.

21415666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 813.

The product of its digits is 8640, while the sum is 31.

The square root of 21415666 is about 4627.7063433195. The cubic root of 21415666 is about 277.7008409978.

The spelling of 21415666 in words is "twenty-one million, four hundred fifteen thousand, six hundred sixty-six".