81661180 has 12 divisors (see below), whose sum is σ = 171488520. Its totient is φ = 32664464.

The previous prime is 81661159. The next prime is 81661189. The reversal of 81661180 is 8116618.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81661189) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2041510 + ... + 2041549.

It is an arithmetic number, because the mean of its divisors is an integer number (14290710).

Almost surely, 2^81661180 is an apocalyptic number.

It is an amenable number.

81661180 is an abundant number, since it is smaller than the sum of its proper divisors (89827340).

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

81661180 is a wasteful number, since it uses less digits than its factorization.

81661180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4083068 (or 4083066 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 81661180 is about 9036.6575679285. The cubic root of 81661180 is about 433.8489496782.

Adding to 81661180 its reverse (8116618), we get a palindrome (89777798).

The spelling of 81661180 in words is "eighty-one million, six hundred sixty-one thousand, one hundred eighty".