161866 has 4 divisors (see below), whose sum is σ = 242802. Its totient is φ = 80932.

The previous prime is 161839. The next prime is 161869. The reversal of 161866 is 668161.

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., 143641 + 18225 = 379^2 + 135^2 .

It is not an unprimeable number, because it can be changed into a prime (161869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40465 + ... + 40468.

2¹⁶¹⁸⁶⁶ is an apocalyptic number.

161866 is a deficient number, since it is larger than the sum of its proper divisors (80936).

161866 is an equidigital number, since it uses as much as digits as its factorization.

161866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80935.

The product of its digits is 1728, while the sum is 28.

The square root of 161866 is about 402.3257386745. The cubic root of 161866 is about 54.4985831352.

The spelling of 161866 in words is "one hundred sixty-one thousand, eight hundred sixty-six".