161665555601 has 16 divisors (see below), whose sum is σ = 178041768768. Its totient is φ = 145569715200.

The previous prime is 161665555559. The next prime is 161665555619. The reversal of 161665555601 is 106555566161.

It is a cyclic number.

It is not a de Polignac number, because 161665555601 - 2¹⁰ = 161665554577 is a prime.

It is a super-2 number, since 2×161665555601² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161665555651) 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, 11095361 + ... + 11109921.

It is an arithmetic number, because the mean of its divisors is an integer number (11127610548).

Almost surely, 2^161665555601 is an apocalyptic number.

161665555601 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

161665555601 is a deficient number, since it is larger than the sum of its proper divisors (16376213167).

161665555601 is a wasteful number, since it uses less digits than its factorization.

161665555601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24112.

The product of its (nonzero) digits is 810000, while the sum is 47.

The spelling of 161665555601 in words is "one hundred sixty-one billion, six hundred sixty-five million, five hundred fifty-five thousand, six hundred one".