166355561 has 2 divisors, whose sum is σ = 166355562. Its totient is φ = 166355560.

The previous prime is 166355543. The next prime is 166355599. The reversal of 166355561 is 165553661.

166355561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (166355599) can be obtained adding 166355561 to its sum of digits (38).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 98803600 + 67551961 = 9940^2 + 8219^2 .

It is a cyclic number.

It is not a de Polignac number, because 166355561 - 2¹⁴ = 166339177 is a prime.

It is not a weakly prime, because it can be changed into another prime (166351561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83177780 + 83177781.

It is an arithmetic number, because the mean of its divisors is an integer number (83177781).

Almost surely, 2^166355561 is an apocalyptic number.

It is an amenable number.

166355561 is a deficient number, since it is larger than the sum of its proper divisors (1).

166355561 is an equidigital number, since it uses as much as digits as its factorization.

166355561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81000, while the sum is 38.

The square root of 166355561 is about 12897.8897886437. The cubic root of 166355561 is about 549.9785787800.

The spelling of 166355561 in words is "one hundred sixty-six million, three hundred fifty-five thousand, five hundred sixty-one".