81304561 has 8 divisors (see below), whose sum is σ = 87635520. Its totient is φ = 74984592.

The previous prime is 81304547. The next prime is 81304571. The reversal of 81304561 is 16540318.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81304561 - 2⁹ = 81304049 is a prime.

It is a super-2 number, since 2×81304561² = 13220863278805442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81304541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19116 + ... + 22978.

It is an arithmetic number, because the mean of its divisors is an integer number (10954440).

Almost surely, 2^81304561 is an apocalyptic number.

It is an amenable number.

81304561 is a deficient number, since it is larger than the sum of its proper divisors (6330959).

81304561 is a wasteful number, since it uses less digits than its factorization.

81304561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5495.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 81304561 is about 9016.9041804823. The cubic root of 81304561 is about 433.2164804580.

Adding to 81304561 its reverse (16540318), we get a palindrome (97844879).

The spelling of 81304561 in words is "eighty-one million, three hundred four thousand, five hundred sixty-one".