161666661 has 8 divisors (see below), whose sum is σ = 232136800. Its totient is φ = 99487152.

The previous prime is 161666641. The next prime is 161666663. The reversal of 161666661 is 166666161.

It is a happy number.

161666661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 161666661 - 2⁵ = 161666629 is a prime.

It is a super-2 number, since 2×161666661² = 52272218557777842, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 4145299 = 161666661 / (1 + 6 + 1 + 6 + 6 + 6 + 6 + 6 + 1).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161666663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2072611 + ... + 2072688.

It is an arithmetic number, because the mean of its divisors is an integer number (29017100).

Almost surely, 2^161666661 is an apocalyptic number.

It is an amenable number.

161666661 is a deficient number, since it is larger than the sum of its proper divisors (70470139).

161666661 is a wasteful number, since it uses less digits than its factorization.

161666661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4145315.

The product of its digits is 46656, while the sum is 39.

The square root of 161666661 is about 12714.8205256700. The cubic root of 161666661 is about 544.7620216226.

The spelling of 161666661 in words is "one hundred sixty-one million, six hundred sixty-six thousand, six hundred sixty-one".