166221778291 has 2 divisors, whose sum is σ = 166221778292. Its totient is φ = 166221778290.

The previous prime is 166221778249. The next prime is 166221778321. The reversal of 166221778291 is 192877122661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 166221778291 - 2⁹ = 166221777779 is a prime.

It is not a weakly prime, because it can be changed into another prime (166221778091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83110889145 + 83110889146.

It is an arithmetic number, because the mean of its divisors is an integer number (83110889146).

Almost surely, 2^166221778291 is an apocalyptic number.

166221778291 is a deficient number, since it is larger than the sum of its proper divisors (1).

166221778291 is an equidigital number, since it uses as much as digits as its factorization.

166221778291 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1016064, while the sum is 52.

The spelling of 166221778291 in words is "one hundred sixty-six billion, two hundred twenty-one million, seven hundred seventy-eight thousand, two hundred ninety-one".