161858 has 4 divisors (see below), whose sum is σ = 242790. Its totient is φ = 80928.

The previous prime is 161839. The next prime is 161869. The reversal of 161858 is 858161.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 124609 + 37249 = 353^2 + 193^2 .

It is an alternating number because its digits alternate between odd and even.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 161858.

It is an unprimeable number.

161858 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 40463 + ... + 40466.

2¹⁶¹⁸⁵⁸ is an apocalyptic number.

161858 is a deficient number, since it is larger than the sum of its proper divisors (80932).

161858 is an equidigital number, since it uses as much as digits as its factorization.

161858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80931.

The product of its digits is 1920, while the sum is 29.

The square root of 161858 is about 402.3157963590. The cubic root of 161858 is about 54.4976852817.

The spelling of 161858 in words is "one hundred sixty-one thousand, eight hundred fifty-eight".