161665110557 has 16 divisors (see below), whose sum is σ = 166296083184. Its totient is φ = 157068288000.

The previous prime is 161665110547. The next prime is 161665110569. The reversal of 161665110557 is 755011566161.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 53706208516 + 107958902041 = 231746^2 + 328571^2 .

It is a cyclic number.

It is not a de Polignac number, because 161665110557 - 2¹⁸ = 161664848413 is a prime.

It is a super-2 number, since 2×161665110557² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161665110517) 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, 9839213 + ... + 9855629.

It is an arithmetic number, because the mean of its divisors is an integer number (10393505199).

Almost surely, 2^161665110557 is an apocalyptic number.

It is an amenable number.

161665110557 is a deficient number, since it is larger than the sum of its proper divisors (4630972627).

161665110557 is a wasteful number, since it uses less digits than its factorization.

161665110557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17440.

The product of its (nonzero) digits is 189000, while the sum is 44.

The spelling of 161665110557 in words is "one hundred sixty-one billion, six hundred sixty-five million, one hundred ten thousand, five hundred fifty-seven".