166121321 has 2 divisors, whose sum is σ = 166121322. Its totient is φ = 166121320.

The previous prime is 166121261. The next prime is 166121339. The reversal of 166121321 is 123121661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 157151296 + 8970025 = 12536^2 + 2995^2 .

It is a cyclic number.

It is not a de Polignac number, because 166121321 - 2¹⁴ = 166104937 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (168121321) 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 as a sum of consecutive naturals, namely, 83060660 + 83060661.

It is an arithmetic number, because the mean of its divisors is an integer number (83060661).

Almost surely, 2^166121321 is an apocalyptic number.

It is an amenable number.

166121321 is a deficient number, since it is larger than the sum of its proper divisors (1).

166121321 is an equidigital number, since it uses as much as digits as its factorization.

166121321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 23.

The square root of 166121321 is about 12888.8060346954. The cubic root of 166121321 is about 549.7203217179.

Adding to 166121321 its reverse (123121661), we get a palindrome (289242982).

The spelling of 166121321 in words is "one hundred sixty-six million, one hundred twenty-one thousand, three hundred twenty-one".