21666167 has 2 divisors, whose sum is σ = 21666168. Its totient is φ = 21666166.

The previous prime is 21666149. The next prime is 21666191. The reversal of 21666167 is 76166612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21666167 - 2¹⁰ = 21665143 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666767) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833083 + 10833084.

It is an arithmetic number, because the mean of its divisors is an integer number (10833084).

Almost surely, 2^21666167 is an apocalyptic number.

21666167 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666167 is an equidigital number, since it uses as much as digits as its factorization.

21666167 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 35.

The square root of 21666167 is about 4654.6930081371. The cubic root of 21666167 is about 278.7794105187.

The spelling of 21666167 in words is "twenty-one million, six hundred sixty-six thousand, one hundred sixty-seven".