166591221 has 8 divisors (see below), whose sum is σ = 233812320. Its totient is φ = 105215472.

The previous prime is 166591219. The next prime is 166591223. The reversal of 166591221 is 122195661.

It is an interprime number because it is at equal distance from previous prime (166591219) and next prime (166591223).

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

It is not a de Polignac number, because 166591221 - 2¹ = 166591219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166591223) 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, 1461270 + ... + 1461383.

It is an arithmetic number, because the mean of its divisors is an integer number (29226540).

Almost surely, 2^166591221 is an apocalyptic number.

It is an amenable number.

166591221 is a deficient number, since it is larger than the sum of its proper divisors (67221099).

166591221 is a wasteful number, since it uses less digits than its factorization.

166591221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2922675.

The product of its digits is 6480, while the sum is 33.

The square root of 166591221 is about 12907.0221584996. The cubic root of 166591221 is about 550.2381569153.

The spelling of 166591221 in words is "one hundred sixty-six million, five hundred ninety-one thousand, two hundred twenty-one".