161278813 has 4 divisors (see below), whose sum is σ = 170765820. Its totient is φ = 151791808.

The previous prime is 161278807. The next prime is 161278861. The reversal of 161278813 is 318872161.

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 75568249 + 85710564 = 8693^2 + 9258^2 .

It is a cyclic number.

It is not a de Polignac number, because 161278813 - 2¹³ = 161270621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161278613) 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, 4743478 + ... + 4743511.

It is an arithmetic number, because the mean of its divisors is an integer number (42691455).

Almost surely, 2^161278813 is an apocalyptic number.

It is an amenable number.

161278813 is a deficient number, since it is larger than the sum of its proper divisors (9487007).

161278813 is an equidigital number, since it uses as much as digits as its factorization.

161278813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9487006.

The product of its digits is 16128, while the sum is 37.

The square root of 161278813 is about 12699.5595592918. The cubic root of 161278813 is about 544.3260338799.

The spelling of 161278813 in words is "one hundred sixty-one million, two hundred seventy-eight thousand, eight hundred thirteen".