81304381 has 4 divisors (see below), whose sum is σ = 81344700. Its totient is φ = 81264064.

The previous prime is 81304367. The next prime is 81304397. The reversal of 81304381 is 18340318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13505625 + 67798756 = 3675^2 + 8234^2 .

It is a cyclic number.

It is not a de Polignac number, because 81304381 - 2¹⁵ = 81271613 is a prime.

It is a super-2 number, since 2×81304381² = 13220804739586322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81304481) 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, 16966 + ... + 21223.

It is an arithmetic number, because the mean of its divisors is an integer number (20336175).

Almost surely, 2^81304381 is an apocalyptic number.

It is an amenable number.

81304381 is a deficient number, since it is larger than the sum of its proper divisors (40319).

81304381 is a wasteful number, since it uses less digits than its factorization.

81304381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40318.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 81304381 is about 9016.8941992240. The cubic root of 81304381 is about 433.2161607588.

Adding to 81304381 its reverse (18340318), we get a palindrome (99644699).

The spelling of 81304381 in words is "eighty-one million, three hundred four thousand, three hundred eighty-one".