165863585621 has 2 divisors, whose sum is σ = 165863585622. Its totient is φ = 165863585620.

The previous prime is 165863585603. The next prime is 165863585689. The reversal of 165863585621 is 126585368561.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 138615480721 + 27248104900 = 372311^2 + 165070^2 .

It is a cyclic number.

It is not a de Polignac number, because 165863585621 - 2¹⁰ = 165863584597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165863585021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82931792810 + 82931792811.

It is an arithmetic number, because the mean of its divisors is an integer number (82931792811).

Almost surely, 2^165863585621 is an apocalyptic number.

It is an amenable number.

165863585621 is a deficient number, since it is larger than the sum of its proper divisors (1).

165863585621 is an equidigital number, since it uses as much as digits as its factorization.

165863585621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368000, while the sum is 56.

The spelling of 165863585621 in words is "one hundred sixty-five billion, eight hundred sixty-three million, five hundred eighty-five thousand, six hundred twenty-one".