161813138 has 4 divisors (see below), whose sum is σ = 242719710. Its totient is φ = 80906568.

The previous prime is 161813137. The next prime is 161813143. The reversal of 161813138 is 831318161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 831318161 = 10303 ⋅80687.

It can be written as a sum of positive squares in only one way, i.e., 110733529 + 51079609 = 10523^2 + 7147^2 .

It is not an unprimeable number, because it can be changed into a prime (161813131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40453283 + ... + 40453286.

Almost surely, 2^161813138 is an apocalyptic number.

161813138 is a deficient number, since it is larger than the sum of its proper divisors (80906572).

161813138 is an equidigital number, since it uses as much as digits as its factorization.

161813138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80906571.

The product of its digits is 3456, while the sum is 32.

The square root of 161813138 is about 12720.5793107075. The cubic root of 161813138 is about 544.9264979572.

The spelling of 161813138 in words is "one hundred sixty-one million, eight hundred thirteen thousand, one hundred thirty-eight".