161531213 has 2 divisors, whose sum is σ = 161531214. Its totient is φ = 161531212.

The previous prime is 161531147. The next prime is 161531273. The reversal of 161531213 is 312135161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 125507209 + 36024004 = 11203^2 + 6002^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161531213 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161531273) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80765606 + 80765607.

It is an arithmetic number, because the mean of its divisors is an integer number (80765607).

Almost surely, 2^161531213 is an apocalyptic number.

It is an amenable number.

161531213 is a deficient number, since it is larger than the sum of its proper divisors (1).

161531213 is an equidigital number, since it uses as much as digits as its factorization.

161531213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 540, while the sum is 23.

The square root of 161531213 is about 12709.4930268678. The cubic root of 161531213 is about 544.6098411169.

Adding to 161531213 its reverse (312135161), we get a palindrome (473666374).

The spelling of 161531213 in words is "one hundred sixty-one million, five hundred thirty-one thousand, two hundred thirteen".