16561181 has 16 divisors (see below), whose sum is σ = 20557824. Its totient is φ = 12991104.

The previous prime is 16561169. The next prime is 16561187. The reversal of 16561181 is 18116561.

It is a de Polignac number, because none of the positive numbers 2^k-16561181 is a prime.

It is a super-2 number, since 2×16561181² = 548545432229522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561187) 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, 10841 + ... + 12273.

It is an arithmetic number, because the mean of its divisors is an integer number (1284864).

Almost surely, 2^16561181 is an apocalyptic number.

It is an amenable number.

16561181 is a deficient number, since it is larger than the sum of its proper divisors (3996643).

16561181 is a wasteful number, since it uses less digits than its factorization.

16561181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1580.

The product of its digits is 1440, while the sum is 29.

The square root of 16561181 is about 4069.5430947466. The cubic root of 16561181 is about 254.8964387879.

The spelling of 16561181 in words is "sixteen million, five hundred sixty-one thousand, one hundred eighty-one".