81305940 has 96 divisors (see below), whose sum is σ = 243169920. Its totient is φ = 20238336.

The previous prime is 81305927. The next prime is 81305941. The reversal of 81305940 is 4950318.

It is a super-2 number, since 2×81305940² = 13221311758567200, which contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 81305898 and 81305907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81305941) 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 31 ways as a sum of consecutive naturals, for example, 82732 + ... + 83708.

It is an arithmetic number, because the mean of its divisors is an integer number (2533020).

Almost surely, 2^81305940 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81305940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (121584960).

81305940 is an abundant number, since it is smaller than the sum of its proper divisors (161863980).

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

81305940 is a wasteful number, since it uses less digits than its factorization.

81305940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1081 (or 1079 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 81305940 is about 9016.9806476448. The cubic root of 81305940 is about 433.2189296939.

The spelling of 81305940 in words is "eighty-one million, three hundred five thousand, nine hundred forty".