81681120 has 144 divisors (see below), whose sum is σ = 281513232. Its totient is φ = 21565440.

The previous prime is 81681097. The next prime is 81681121. The reversal of 81681120 is 2118618.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81681121) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 188424 + ... + 188856.

It is an arithmetic number, because the mean of its divisors is an integer number (1954953).

Almost surely, 2^81681120 is an apocalyptic number.

81681120 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81681120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (140756616).

81681120 is an abundant number, since it is smaller than the sum of its proper divisors (199832112).

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

81681120 is a wasteful number, since it uses less digits than its factorization.

81681120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 585 (or 574 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 81681120 is about 9037.7607846192. The cubic root of 81681120 is about 433.8842591689.

Adding to 81681120 its reverse (2118618), we get a palindrome (83799738).

The spelling of 81681120 in words is "eighty-one million, six hundred eighty-one thousand, one hundred twenty".