21666207 has 8 divisors (see below), whose sum is σ = 30144384. Its totient is φ = 13816088.

The previous prime is 21666191. The next prime is 21666209. The reversal of 21666207 is 70266612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21666207 - 2⁴ = 21666191 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666209) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156933 + ... + 157070.

It is an arithmetic number, because the mean of its divisors is an integer number (3768048).

Almost surely, 2^21666207 is an apocalyptic number.

21666207 is a deficient number, since it is larger than the sum of its proper divisors (8478177).

21666207 is a wasteful number, since it uses less digits than its factorization.

21666207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 314029.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 21666207 is about 4654.6973048739. The cubic root of 21666207 is about 278.7795820791.

The spelling of 21666207 in words is "twenty-one million, six hundred sixty-six thousand, two hundred seven".