166665557 has 2 divisors, whose sum is σ = 166665558. Its totient is φ = 166665556.

The previous prime is 166665539. The next prime is 166665559. The reversal of 166665557 is 755566661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 122456356 + 44209201 = 11066^2 + 6649^2 .

It is an emirp because it is prime and its reverse (755566661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 166665557 - 2⁶ = 166665493 is a prime.

Together with 166665559, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166665559) 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, 83332778 + 83332779.

It is an arithmetic number, because the mean of its divisors is an integer number (83332779).

Almost surely, 2^166665557 is an apocalyptic number.

It is an amenable number.

166665557 is a deficient number, since it is larger than the sum of its proper divisors (1).

166665557 is an equidigital number, since it uses as much as digits as its factorization.

166665557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1134000, while the sum is 47.

The square root of 166665557 is about 12909.9015100813. The cubic root of 166665557 is about 550.3199868002.

The spelling of 166665557 in words is "one hundred sixty-six million, six hundred sixty-five thousand, five hundred fifty-seven".