165811025601 has 81 divisors (see below), whose sum is σ = 265679680539. Its totient is φ = 99604132992.

The previous prime is 165811025587. The next prime is 165811025657. The reversal of 165811025601 is 106520118561.

The square root of 165811025601 is 407199.

It is a perfect power (a square), and thus also a powerful number.

165811025601 is a `hidden beast` number, since 1 + 6 + 5 + 81 + 10 + 2 + 560 + 1 = 666.

It can be written as a sum of positive squares in 13 ways, for example, as 14897423025 + 150913602576 = 122055^2 + 388476^2 .

It is not a de Polignac number, because 165811025601 - 2⁹ = 165811025089 is a prime.

It is a super-2 number, since 2×165811025601² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (165811025671) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 841680235 + ... + 841680431.

Almost surely, 2^165811025601 is an apocalyptic number.

165811025601 is the 407199-th square number.

165811025601 is the 203600-th centered octagonal number.

It is an amenable number.

165811025601 is a deficient number, since it is larger than the sum of its proper divisors (99868654938).

165811025601 is an equidigital number, since it uses as much as digits as its factorization.

165811025601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532 (or 266 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 36.

Multiplying 165811025601 by its sum of digits (36), we get a square (5969196921636 = 2443194²).

The spelling of 165811025601 in words is "one hundred sixty-five billion, eight hundred eleven million, twenty-five thousand, six hundred one".