166581881 has 4 divisors (see below), whose sum is σ = 171084132. Its totient is φ = 162079632.

The previous prime is 166581869. The next prime is 166581901. The reversal of 166581881 is 188185661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 188185661 = 283 ⋅664967.

It can be written as a sum of positive squares in 2 ways, for example, as 127893481 + 38688400 = 11309^2 + 6220^2 .

It is a cyclic number.

It is not a de Polignac number, because 166581881 - 2¹⁰ = 166580857 is a prime.

It is a super-2 number, since 2×166581881² = 55499046154996322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166586881) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2251070 + ... + 2251143.

It is an arithmetic number, because the mean of its divisors is an integer number (42771033).

Almost surely, 2^166581881 is an apocalyptic number.

It is an amenable number.

166581881 is a deficient number, since it is larger than the sum of its proper divisors (4502251).

166581881 is an equidigital number, since it uses as much as digits as its factorization.

166581881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4502250.

The product of its digits is 92160, while the sum is 44.

The square root of 166581881 is about 12906.6603348814. The cubic root of 166581881 is about 550.2278736194.

The spelling of 166581881 in words is "one hundred sixty-six million, five hundred eighty-one thousand, eight hundred eighty-one".