161640081 has 12 divisors (see below), whose sum is σ = 239175300. Its totient is φ = 105131520.

The previous prime is 161640071. The next prime is 161640103. The reversal of 161640081 is 180046161.

161640081 is a `hidden beast` number, since 1 + 616 + 40 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 79121025 + 82519056 = 8895^2 + 9084^2 .

It is not a de Polignac number, because 161640081 - 2¹⁰ = 161639057 is a prime.

It is a super-2 number, since 2×161640081² = 52255031571373122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161640001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 218656 + ... + 219393.

It is an arithmetic number, because the mean of its divisors is an integer number (19931275).

Almost surely, 2^161640081 is an apocalyptic number.

It is an amenable number.

161640081 is a deficient number, since it is larger than the sum of its proper divisors (77535219).

161640081 is a wasteful number, since it uses less digits than its factorization.

161640081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438096 (or 438093 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 161640081 is about 12713.7752457718. The cubic root of 161640081 is about 544.7321647800.

The spelling of 161640081 in words is "one hundred sixty-one million, six hundred forty thousand, eighty-one".