161665555599 has 24 divisors (see below), whose sum is σ = 242171794800. Its totient is φ = 103801017600.

The previous prime is 161665555559. The next prime is 161665555619. The reversal of 161665555599 is 995555566161.

It is a happy number.

161665555599 is a `hidden beast` number, since 1 + 6 + 16 + 65 + 5 + 5 + 559 + 9 = 666.

It is not a de Polignac number, because 161665555599 - 2⁹ = 161665555087 is a prime.

It is a super-2 number, since 2×161665555599² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161665555559) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 667669 + ... + 876990.

It is an arithmetic number, because the mean of its divisors is an integer number (10090491450).

Almost surely, 2^161665555599 is an apocalyptic number.

161665555599 is a deficient number, since it is larger than the sum of its proper divisors (80506239201).

161665555599 is a wasteful number, since it uses less digits than its factorization.

161665555599 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1545095 (or 1545092 counting only the distinct ones).

The product of its digits is 54675000, while the sum is 63.

The spelling of 161665555599 in words is "one hundred sixty-one billion, six hundred sixty-five million, five hundred fifty-five thousand, five hundred ninety-nine".