81504481 has 4 divisors (see below), whose sum is σ = 81954964. Its totient is φ = 81054000.

The previous prime is 81504463. The next prime is 81504491. The reversal of 81504481 is 18440518.

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 234256 + 81270225 = 484^2 + 9015^2 .

It is a cyclic number.

It is not a de Polignac number, because 81504481 - 2¹¹ = 81502433 is a prime.

It is a super-2 number, since 2×81504481² = 13285960846158722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81504421) 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, 224970 + ... + 225331.

It is an arithmetic number, because the mean of its divisors is an integer number (20488741).

Almost surely, 2^81504481 is an apocalyptic number.

It is an amenable number.

81504481 is a deficient number, since it is larger than the sum of its proper divisors (450483).

81504481 is a wasteful number, since it uses less digits than its factorization.

81504481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450482.

The product of its (nonzero) digits is 5120, while the sum is 31.

The square root of 81504481 is about 9027.9832188590. The cubic root of 81504481 is about 433.5712688697.

Adding to 81504481 its reverse (18440518), we get a palindrome (99944999).

The spelling of 81504481 in words is "eighty-one million, five hundred four thousand, four hundred eighty-one".