166201661 has 4 divisors (see below), whose sum is σ = 167847324. Its totient is φ = 164556000.

The previous prime is 166201631. The next prime is 166201681. The reversal of 166201661 is 166102661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166102661 = 719 ⋅231019.

It can be written as a sum of positive squares in 2 ways, for example, as 94206436 + 71995225 = 9706^2 + 8485^2 .

It is a cyclic number.

It is not a de Polignac number, because 166201661 - 2⁶ = 166201597 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 (166201631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 822680 + ... + 822881.

It is an arithmetic number, because the mean of its divisors is an integer number (41961831).

Almost surely, 2^166201661 is an apocalyptic number.

It is an amenable number.

166201661 is a deficient number, since it is larger than the sum of its proper divisors (1645663).

166201661 is a wasteful number, since it uses less digits than its factorization.

166201661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1645662.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 166201661 is about 12891.9223159310. The cubic root of 166201661 is about 549.8089264650.

It can be divided in two parts, 16620 and 1661, that added together give a palindrome (18281).

The spelling of 166201661 in words is "one hundred sixty-six million, two hundred one thousand, six hundred sixty-one".