161921158723 has 4 divisors (see below), whose sum is σ = 161960378440. Its totient is φ = 161881939008.

The previous prime is 161921158703. The next prime is 161921158727. The reversal of 161921158723 is 327851129161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 327851129161 = 313 ⋅1047447697.

It is a cyclic number.

It is not a de Polignac number, because 161921158723 - 2⁵ = 161921158691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161921158727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19603665 + ... + 19611922.

It is an arithmetic number, because the mean of its divisors is an integer number (40490094610).

Almost surely, 2^161921158723 is an apocalyptic number.

161921158723 is a deficient number, since it is larger than the sum of its proper divisors (39219717).

161921158723 is an equidigital number, since it uses as much as digits as its factorization.

161921158723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39219716.

The product of its digits is 181440, while the sum is 46.

The spelling of 161921158723 in words is "one hundred sixty-one billion, nine hundred twenty-one million, one hundred fifty-eight thousand, seven hundred twenty-three".