166412221 has 2 divisors, whose sum is σ = 166412222. Its totient is φ = 166412220.

The previous prime is 166412219. The next prime is 166412227. The reversal of 166412221 is 122214661.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 150332121 + 16080100 = 12261^2 + 4010^2 .

It is a cyclic number.

It is not a de Polignac number, because 166412221 - 2¹ = 166412219 is a prime.

Together with 166412219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166412227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83206110 + 83206111.

It is an arithmetic number, because the mean of its divisors is an integer number (83206111).

Almost surely, 2^166412221 is an apocalyptic number.

It is an amenable number.

166412221 is a deficient number, since it is larger than the sum of its proper divisors (1).

166412221 is an equidigital number, since it uses as much as digits as its factorization.

166412221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 25.

The square root of 166412221 is about 12900.0860849841. The cubic root of 166412221 is about 550.0410118178.

Adding to 166412221 its reverse (122214661), we get a palindrome (288626882).

The spelling of 166412221 in words is "one hundred sixty-six million, four hundred twelve thousand, two hundred twenty-one".