166531 has 4 divisors (see below), whose sum is σ = 167464. Its totient is φ = 165600.

The previous prime is 166487. The next prime is 166541. The reversal of 166531 is 135661.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 166531 - 2⁷ = 166403 is a prime.

It is a super-2 number, since 2×166531² = 55465147922, which contains 22 as substring.

It is a Duffinian number.

166531 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (166541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105 + ... + 586.

It is an arithmetic number, because the mean of its divisors is an integer number (41866).

2¹⁶⁶⁵³¹ is an apocalyptic number.

166531 is the 183-rd centered decagonal number.

166531 is a deficient number, since it is larger than the sum of its proper divisors (933).

166531 is an equidigital number, since it uses as much as digits as its factorization.

166531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 932.

The product of its digits is 540, while the sum is 22.

The square root of 166531 is about 408.0820995829. The cubic root of 166531 is about 55.0171847127.

It can be divided in two parts, 1665 and 31, that multiplied together give a palindrome (51615).

The spelling of 166531 in words is "one hundred sixty-six thousand, five hundred thirty-one".