161537077781 has 2 divisors, whose sum is σ = 161537077782. Its totient is φ = 161537077780.

The previous prime is 161537077777. The next prime is 161537077811. The reversal of 161537077781 is 187770735161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 154186587556 + 7350490225 = 392666^2 + 85735^2 .

It is a cyclic number.

It is not a de Polignac number, because 161537077781 - 2² = 161537077777 is a prime.

It is a super-2 number, since 2×161537077781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161537077081) 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 as a sum of consecutive naturals, namely, 80768538890 + 80768538891.

It is an arithmetic number, because the mean of its divisors is an integer number (80768538891).

Almost surely, 2^161537077781 is an apocalyptic number.

It is an amenable number.

161537077781 is a deficient number, since it is larger than the sum of its proper divisors (1).

161537077781 is an equidigital number, since it uses as much as digits as its factorization.

161537077781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728720, while the sum is 53.

The spelling of 161537077781 in words is "one hundred sixty-one billion, five hundred thirty-seven million, seventy-seven thousand, seven hundred eighty-one".