666506161 has 4 divisors (see below), whose sum is σ = 666579312. Its totient is φ = 666433012.

The previous prime is 666506041. The next prime is 666506189. The reversal of 666506161 is 161605666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, 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 666506161 - 2¹⁷ = 666375089 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666506161.

It is not an unprimeable number, because it can be changed into a prime (666506261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20575 + ... + 41908.

It is an arithmetic number, because the mean of its divisors is an integer number (166644828).

Almost surely, 2^666506161 is an apocalyptic number.

It is an amenable number.

666506161 is a deficient number, since it is larger than the sum of its proper divisors (73151).

666506161 is a wasteful number, since it uses less digits than its factorization.

666506161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73150.

The product of its (nonzero) digits is 38880, while the sum is 37.

The square root of 666506161 is about 25816.7806087436. The cubic root of 666506161 is about 873.5103518018.

The spelling of 666506161 in words is "six hundred sixty-six million, five hundred six thousand, one hundred sixty-one".