161556332813 has 2 divisors, whose sum is σ = 161556332814. Its totient is φ = 161556332812.

The previous prime is 161556332807. The next prime is 161556332831. The reversal of 161556332813 is 318233655161.

Together with next prime (161556332831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 113891400484 + 47664932329 = 337478^2 + 218323^2 .

It is a cyclic number.

It is not a de Polignac number, because 161556332813 - 2¹⁶ = 161556267277 is a prime.

It is a super-2 number, since 2×161556332813² (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 (161556332863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80778166406 + 80778166407.

It is an arithmetic number, because the mean of its divisors is an integer number (80778166407).

Almost surely, 2^161556332813 is an apocalyptic number.

It is an amenable number.

161556332813 is a deficient number, since it is larger than the sum of its proper divisors (1).

161556332813 is an equidigital number, since it uses as much as digits as its factorization.

161556332813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 388800, while the sum is 44.

Adding to 161556332813 its reverse (318233655161), we get a palindrome (479789987974).

The spelling of 161556332813 in words is "one hundred sixty-one billion, five hundred fifty-six million, three hundred thirty-two thousand, eight hundred thirteen".