166648721 has 2 divisors, whose sum is σ = 166648722. Its totient is φ = 166648720.

The previous prime is 166648717. The next prime is 166648733. The reversal of 166648721 is 127846661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 88078225 + 78570496 = 9385^2 + 8864^2 .

It is an emirp because it is prime and its reverse (127846661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 166648721 - 2² = 166648717 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (166648771) 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, 83324360 + 83324361.

It is an arithmetic number, because the mean of its divisors is an integer number (83324361).

Almost surely, 2^166648721 is an apocalyptic number.

It is an amenable number.

166648721 is a deficient number, since it is larger than the sum of its proper divisors (1).

166648721 is an equidigital number, since it uses as much as digits as its factorization.

166648721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96768, while the sum is 41.

The square root of 166648721 is about 12909.2494359664. The cubic root of 166648721 is about 550.3014556782.

The spelling of 166648721 in words is "one hundred sixty-six million, six hundred forty-eight thousand, seven hundred twenty-one".