161878121 has 2 divisors, whose sum is σ = 161878122. Its totient is φ = 161878120.

The previous prime is 161878109. The next prime is 161878139. The reversal of 161878121 is 121878161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 133148521 + 28729600 = 11539^2 + 5360^2 .

It is an emirp because it is prime and its reverse (121878161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161878121 - 2¹⁴ = 161861737 is a prime.

It is a Sophie Germain prime.

It is an alternating number because its digits alternate between odd and even.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (161878181) 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, 80939060 + 80939061.

It is an arithmetic number, because the mean of its divisors is an integer number (80939061).

Almost surely, 2^161878121 is an apocalyptic number.

It is an amenable number.

161878121 is a deficient number, since it is larger than the sum of its proper divisors (1).

161878121 is an equidigital number, since it uses as much as digits as its factorization.

161878121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5376, while the sum is 35.

The square root of 161878121 is about 12723.1333011959. The cubic root of 161878121 is about 544.9994343905. Note that the first 3 decimals are identical.

The spelling of 161878121 in words is "one hundred sixty-one million, eight hundred seventy-eight thousand, one hundred twenty-one".