166261221 has 16 divisors (see below), whose sum is σ = 281500800. Its totient is φ = 95006304.

The previous prime is 166261213. The next prime is 166261243. The reversal of 166261221 is 122162661.

166261221 is a `hidden beast` number, since 1 + 6 + 626 + 12 + 21 = 666.

It is not a de Polignac number, because 166261221 - 2³ = 166261213 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166261211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 439656 + ... + 440033.

It is an arithmetic number, because the mean of its divisors is an integer number (17593800).

Almost surely, 2^166261221 is an apocalyptic number.

It is an amenable number.

166261221 is a deficient number, since it is larger than the sum of its proper divisors (115239579).

166261221 is an equidigital number, since it uses as much as digits as its factorization.

166261221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 879705 (or 879699 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 166261221 is about 12894.2320826019. The cubic root of 166261221 is about 549.8745951002.

The spelling of 166261221 in words is "one hundred sixty-six million, two hundred sixty-one thousand, two hundred twenty-one".