166421616660605 has 4 divisors (see below), whose sum is σ = 199705939992732. Its totient is φ = 133137293328480.

The previous prime is 166421616660587. The next prime is 166421616660667. The reversal of 166421616660605 is 506066616124661.

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 110581776229369 + 55839840431236 = 10515787^2 + 7472606^2 .

It is not a de Polignac number, because 166421616660605 - 2¹⁰ = 166421616659581 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16642161666056 + ... + 16642161666065.

It is an arithmetic number, because the mean of its divisors is an integer number (49926484998183).

Almost surely, 2^{166421616660605} is an apocalyptic number.

It is an amenable number.

166421616660605 is a deficient number, since it is larger than the sum of its proper divisors (33284323332127).

166421616660605 is an equidigital number, since it uses as much as digits as its factorization.

166421616660605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33284323332126.

The product of its (nonzero) digits is 11197440, while the sum is 56.

The spelling of 166421616660605 in words is "one hundred sixty-six trillion, four hundred twenty-one billion, six hundred sixteen million, six hundred sixty thousand, six hundred five".