166654781 has 2 divisors, whose sum is σ = 166654782. Its totient is φ = 166654780.

The previous prime is 166654777. The next prime is 166654783. The reversal of 166654781 is 187456661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 166152100 + 502681 = 12890^2 + 709^2 .

It is a cyclic number.

It is not a de Polignac number, because 166654781 - 2² = 166654777 is a prime.

It is a super-2 number, since 2×166654781² = 55547632060315922, which contains 22 as substring.

Together with 166654783, 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 (166654783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83327390 + 83327391.

It is an arithmetic number, because the mean of its divisors is an integer number (83327391).

Almost surely, 2^166654781 is an apocalyptic number.

It is an amenable number.

166654781 is a deficient number, since it is larger than the sum of its proper divisors (1).

166654781 is an equidigital number, since it uses as much as digits as its factorization.

166654781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 44.

The square root of 166654781 is about 12909.4841492602. The cubic root of 166654781 is about 550.3081259692.

The spelling of 166654781 in words is "one hundred sixty-six million, six hundred fifty-four thousand, seven hundred eighty-one".