161538198997709 has 4 divisors (see below), whose sum is σ = 161810607428316. Its totient is φ = 161265790567104.

The previous prime is 161538198997639. The next prime is 161538198997723. The reversal of 161538198997709 is 907799891835161.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 92495344502500 + 69042854495209 = 9617450^2 + 8309203^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161538198997709 is a prime.

It is a super-3 number, since 3×161538198997709³ (a number of 44 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161538198927709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136204214414 + ... + 136204215599.

It is an arithmetic number, because the mean of its divisors is an integer number (40452651857079).

Almost surely, 2^{161538198997709} is an apocalyptic number.

It is an amenable number.

161538198997709 is a deficient number, since it is larger than the sum of its proper divisors (272408430607).

161538198997709 is an equidigital number, since it uses as much as digits as its factorization.

161538198997709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272408430606.

The product of its (nonzero) digits is 1851776640, while the sum is 83.

The spelling of 161538198997709 in words is "one hundred sixty-one trillion, five hundred thirty-eight billion, one hundred ninety-eight million, nine hundred ninety-seven thousand, seven hundred nine".