161221334165 has 4 divisors (see below), whose sum is σ = 193465601004. Its totient is φ = 128977067328.

The previous prime is 161221334159. The next prime is 161221334269. The reversal of 161221334165 is 561433122161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 561433122161 = 167 ⋅3361874983.

It can be written as a sum of positive squares in 2 ways, for example, as 36836741041 + 124384593124 = 191929^2 + 352682^2 .

It is a cyclic number.

It is not a de Polignac number, because 161221334165 - 2⁴ = 161221334149 is a prime.

It is a super-3 number, since 3×161221334165³ (a number of 35 digits) contains 333 as substring.

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, 16122133412 + ... + 16122133421.

It is an arithmetic number, because the mean of its divisors is an integer number (48366400251).

Almost surely, 2^161221334165 is an apocalyptic number.

It is an amenable number.

161221334165 is a deficient number, since it is larger than the sum of its proper divisors (32244266839).

161221334165 is an equidigital number, since it uses as much as digits as its factorization.

161221334165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32244266838.

The product of its digits is 25920, while the sum is 35.

The spelling of 161221334165 in words is "one hundred sixty-one billion, two hundred twenty-one million, three hundred thirty-four thousand, one hundred sixty-five".