161581 has 8 divisors (see below), whose sum is σ = 189504. Its totient is φ = 134880.

The previous prime is 161573. The next prime is 161591. The reversal of 161581 is 185161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 161581 - 2³ = 161573 is a prime.

It is a super-2 number, since 2×161581² = 52216839122, which contains 22 as substring.

161581 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6 + ... + 568.

It is an arithmetic number, because the mean of its divisors is an integer number (23688).

2¹⁶¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

161581 is a deficient number, since it is larger than the sum of its proper divisors (27923).

161581 is an equidigital number, since it uses as much as digits as its factorization.

161581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 611.

The product of its digits is 240, while the sum is 22.

The square root of 161581 is about 401.9713920169. The cubic root of 161581 is about 54.4665788415.

The spelling of 161581 in words is "one hundred sixty-one thousand, five hundred eighty-one".