165684207721 has 16 divisors (see below), whose sum is σ = 175429800000. Its totient is φ = 156041669376.

The previous prime is 165684207701. The next prime is 165684207737. The reversal of 165684207721 is 127702486561.

It is a cyclic number.

It is not a de Polignac number, because 165684207721 - 2¹³ = 165684199529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165684207701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19888285 + ... + 19896613.

It is an arithmetic number, because the mean of its divisors is an integer number (10964362500).

Almost surely, 2^165684207721 is an apocalyptic number.

It is an amenable number.

165684207721 is a deficient number, since it is larger than the sum of its proper divisors (9745592279).

165684207721 is a wasteful number, since it uses less digits than its factorization.

165684207721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14376.

The product of its (nonzero) digits is 1128960, while the sum is 49.

The spelling of 165684207721 in words is "one hundred sixty-five billion, six hundred eighty-four million, two hundred seven thousand, seven hundred twenty-one".