166561651 has 2 divisors, whose sum is σ = 166561652. Its totient is φ = 166561650.

The previous prime is 166561649. The next prime is 166561673. The reversal of 166561651 is 156165661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 166561651 - 2¹ = 166561649 is a prime.

Together with 166561649, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 166561651.

It is not a weakly prime, because it can be changed into another prime (166561751) 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, 83280825 + 83280826.

It is an arithmetic number, because the mean of its divisors is an integer number (83280826).

Almost surely, 2^166561651 is an apocalyptic number.

166561651 is a deficient number, since it is larger than the sum of its proper divisors (1).

166561651 is an equidigital number, since it uses as much as digits as its factorization.

166561651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 37.

The square root of 166561651 is about 12905.8766071895. The cubic root of 166561651 is about 550.2055991671.

The spelling of 166561651 in words is "one hundred sixty-six million, five hundred sixty-one thousand, six hundred fifty-one".