21187066 has 16 divisors (see below), whose sum is σ = 33865344. Its totient is φ = 9906624.

The previous prime is 21187063. The next prime is 21187079. The reversal of 21187066 is 66078112.

It is not an unprimeable number, because it can be changed into a prime (21187063) 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, 3631 + ... + 7453.

It is an arithmetic number, because the mean of its divisors is an integer number (2116584).

Almost surely, 2^21187066 is an apocalyptic number.

21187066 is a deficient number, since it is larger than the sum of its proper divisors (12678278).

21187066 is a wasteful number, since it uses less digits than its factorization.

21187066 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4005.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21187066 is about 4602.9410163503. The cubic root of 21187066 is about 276.7092049236.

The spelling of 21187066 in words is "twenty-one million, one hundred eighty-seven thousand, sixty-six".