21666727 has 4 divisors (see below), whose sum is σ = 21727440. Its totient is φ = 21606016.

The previous prime is 21666709. The next prime is 21666731. The reversal of 21666727 is 72766612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21666727 - 2¹⁹ = 21142439 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666767) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29818 + ... + 30535.

It is an arithmetic number, because the mean of its divisors is an integer number (5431860).

Almost surely, 2^21666727 is an apocalyptic number.

21666727 is a deficient number, since it is larger than the sum of its proper divisors (60713).

21666727 is an equidigital number, since it uses as much as digits as its factorization.

21666727 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60712.

The product of its digits is 42336, while the sum is 37.

The square root of 21666727 is about 4654.7531620914. The cubic root of 21666727 is about 278.7818123452.

The spelling of 21666727 in words is "twenty-one million, six hundred sixty-six thousand, seven hundred twenty-seven".