21666135 has 16 divisors (see below), whose sum is σ = 35321184. Its totient is φ = 11336832.

The previous prime is 21666121. The next prime is 21666149. The reversal of 21666135 is 53166612.

It is an interprime number because it is at equal distance from previous prime (21666121) and next prime (21666149).

It is not a de Polignac number, because 21666135 - 2⁸ = 21665879 is a prime.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 12832 + ... + 14421.

It is an arithmetic number, because the mean of its divisors is an integer number (2207574).

Almost surely, 2^21666135 is an apocalyptic number.

21666135 is a deficient number, since it is larger than the sum of its proper divisors (13655049).

21666135 is a wasteful number, since it uses less digits than its factorization.

21666135 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27314.

The product of its digits is 6480, while the sum is 30.

The square root of 21666135 is about 4654.6895707448. The cubic root of 21666135 is about 278.7792732702.

The spelling of 21666135 in words is "twenty-one million, six hundred sixty-six thousand, one hundred thirty-five".