166616556650561 has 4 divisors (see below), whose sum is σ = 166704203447124. Its totient is φ = 166528909854000.

The previous prime is 166616556650527. The next prime is 166616556650573. The reversal of 166616556650561 is 165056655616661.

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

It can be written as a sum of positive squares in 2 ways, for example, as 29304563930161 + 137311992720400 = 5413369^2 + 11718020^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-166616556650561 is a prime.

It is a super-3 number, since 3×166616556650561³ (a number of 44 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166616556650261) 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, 43823395430 + ... + 43823399231.

It is an arithmetic number, because the mean of its divisors is an integer number (41676050861781).

Almost surely, 2^{166616556650561} is an apocalyptic number.

It is an amenable number.

166616556650561 is a deficient number, since it is larger than the sum of its proper divisors (87646796563).

166616556650561 is an equidigital number, since it uses as much as digits as its factorization.

166616556650561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87646796562.

The product of its (nonzero) digits is 174960000, while the sum is 65.

The spelling of 166616556650561 in words is "one hundred sixty-six trillion, six hundred sixteen billion, five hundred fifty-six million, six hundred fifty thousand, five hundred sixty-one".