81304320 has 144 divisors (see below), whose sum is σ = 268434432. Its totient is φ = 20951040.

The previous prime is 81304303. The next prime is 81304343. The reversal of 81304320 is 2340318.

It is a happy number.

It is a super-2 number, since 2×81304320² = 13220784901324800, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 118699 + ... + 119381.

It is an arithmetic number, because the mean of its divisors is an integer number (1864128).

Almost surely, 2^81304320 is an apocalyptic number.

81304320 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 81304320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134217216).

81304320 is an abundant number, since it is smaller than the sum of its proper divisors (187130112).

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

81304320 is a wasteful number, since it uses less digits than its factorization.

81304320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738 (or 724 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 81304320 is about 9016.8908166840. The cubic root of 81304320 is about 433.2160524161.

Adding to 81304320 its reverse (2340318), we get a palindrome (83644638).

The spelling of 81304320 in words is "eighty-one million, three hundred four thousand, three hundred twenty".