165601051605661 has 4 divisors (see below), whose sum is σ = 189258344692192. Its totient is φ = 141943758519132.

The previous prime is 165601051605557. The next prime is 165601051605713. The reversal of 165601051605661 is 166506150106561.

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.

It is a cyclic number.

It is not a de Polignac number, because 165601051605661 - 2⁷ = 165601051605533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165601051695661) 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, 11828646543255 + ... + 11828646543268.

It is an arithmetic number, because the mean of its divisors is an integer number (47314586173048).

Almost surely, 2^{165601051605661} is an apocalyptic number.

It is an amenable number.

165601051605661 is a deficient number, since it is larger than the sum of its proper divisors (23657293086531).

165601051605661 is an equidigital number, since it uses as much as digits as its factorization.

165601051605661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23657293086530.

The product of its (nonzero) digits is 972000, while the sum is 49.

The spelling of 165601051605661 in words is "one hundred sixty-five trillion, six hundred one billion, fifty-one million, six hundred five thousand, six hundred sixty-one".