161916396781 has 4 divisors (see below), whose sum is σ = 162281896992. Its totient is φ = 161550896572.

The previous prime is 161916396749. The next prime is 161916396787. The reversal of 161916396781 is 187693619161.

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, and also an emirpimes, since its reverse is a distinct semiprime: 187693619161 = 277 ⋅677594293.

It is a cyclic number.

It is not a de Polignac number, because 161916396781 - 2⁵ = 161916396749 is a prime.

It is a super-2 number, since 2×161916396781² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161916396787) 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, 182749441 + ... + 182750326.

It is an arithmetic number, because the mean of its divisors is an integer number (40570474248).

Almost surely, 2^161916396781 is an apocalyptic number.

It is an amenable number.

161916396781 is a deficient number, since it is larger than the sum of its proper divisors (365500211).

161916396781 is an equidigital number, since it uses as much as digits as its factorization.

161916396781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 365500210.

The product of its digits is 2939328, while the sum is 58.

The spelling of 161916396781 in words is "one hundred sixty-one billion, nine hundred sixteen million, three hundred ninety-six thousand, seven hundred eighty-one".