161506581 has 16 divisors (see below), whose sum is σ = 221153856. Its totient is φ = 104783616.

The previous prime is 161506567. The next prime is 161506607. The reversal of 161506581 is 185605161.

It is not a de Polignac number, because 161506581 - 2¹¹ = 161504533 is a prime.

It is a super-2 number, since 2×161506581² = 52168751412619122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161506181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35661 + ... + 39933.

It is an arithmetic number, because the mean of its divisors is an integer number (13822116).

Almost surely, 2^161506581 is an apocalyptic number.

It is an amenable number.

161506581 is a deficient number, since it is larger than the sum of its proper divisors (59647275).

161506581 is a wasteful number, since it uses less digits than its factorization.

161506581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4612.

The product of its (nonzero) digits is 7200, while the sum is 33.

The square root of 161506581 is about 12708.5239504830. The cubic root of 161506581 is about 544.5821570731.

The spelling of 161506581 in words is "one hundred sixty-one million, five hundred six thousand, five hundred eighty-one".