163651561 has 2 divisors, whose sum is σ = 163651562. Its totient is φ = 163651560.

The previous prime is 163651559. The next prime is 163651577. The reversal of 163651561 is 165156361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 160909225 + 2742336 = 12685^2 + 1656^2 .

It is a cyclic number.

It is not a de Polignac number, because 163651561 - 2¹ = 163651559 is a prime.

Together with 163651559, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (163651531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81825780 + 81825781.

It is an arithmetic number, because the mean of its divisors is an integer number (81825781).

Almost surely, 2^163651561 is an apocalyptic number.

It is an amenable number.

163651561 is a deficient number, since it is larger than the sum of its proper divisors (1).

163651561 is an equidigital number, since it uses as much as digits as its factorization.

163651561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16200, while the sum is 34.

The square root of 163651561 is about 12792.6369838278. The cubic root of 163651561 is about 546.9824398040.

The spelling of 163651561 in words is "one hundred sixty-three million, six hundred fifty-one thousand, five hundred sixty-one".