81561180 has 48 divisors (see below), whose sum is σ = 231275520. Its totient is φ = 21473088.

The previous prime is 81561163. The next prime is 81561229. The reversal of 81561180 is 8116518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 3864 + ... + 13343.

It is an arithmetic number, because the mean of its divisors is an integer number (4818240).

Almost surely, 2^81561180 is an apocalyptic number.

It is an amenable number.

81561180 is an abundant number, since it is smaller than the sum of its proper divisors (149714340).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81561180 is a wasteful number, since it uses less digits than its factorization.

81561180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17298 (or 17296 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 30.

The square root of 81561180 is about 9031.1228537763. The cubic root of 81561180 is about 433.6717842395.

Adding to 81561180 its reverse (8116518), we get a palindrome (89677698).

The spelling of 81561180 in words is "eighty-one million, five hundred sixty-one thousand, one hundred eighty".