166999221 has 6 divisors (see below), whose sum is σ = 241221110. Its totient is φ = 111332808.

The previous prime is 166999219. The next prime is 166999223. The reversal of 166999221 is 122999661.

It is an interprime number because it is at equal distance from previous prime (166999219) and next prime (166999223).

It can be written as a sum of positive squares in only one way, i.e., 129618225 + 37380996 = 11385^2 + 6114^2 .

It is not a de Polignac number, because 166999221 - 2¹ = 166999219 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 (166999223) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9277726 + ... + 9277743.

Almost surely, 2^166999221 is an apocalyptic number.

It is an amenable number.

166999221 is a deficient number, since it is larger than the sum of its proper divisors (74221889).

166999221 is a wasteful number, since it uses less digits than its factorization.

166999221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18555475 (or 18555472 counting only the distinct ones).

The product of its digits is 104976, while the sum is 45.

The square root of 166999221 is about 12922.8178428700. The cubic root of 166999221 is about 550.6869883783.

The spelling of 166999221 in words is "one hundred sixty-six million, nine hundred ninety-nine thousand, two hundred twenty-one".