81533765 has 8 divisors (see below), whose sum is σ = 98809848. Its totient is φ = 64580800.

The previous prime is 81533747. The next prime is 81533791. The reversal of 81533765 is 56733518.

It can be written as a sum of positive squares in 4 ways, for example, as 46226401 + 35307364 = 6799^2 + 5942^2 .

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

It is not a de Polignac number, because 81533765 - 2⁸ = 81533509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80222 + ... + 81231.

It is an arithmetic number, because the mean of its divisors is an integer number (12351231).

Almost surely, 2^81533765 is an apocalyptic number.

It is an amenable number.

81533765 is a deficient number, since it is larger than the sum of its proper divisors (17276083).

81533765 is a wasteful number, since it uses less digits than its factorization.

81533765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161559.

The product of its digits is 75600, while the sum is 38.

The square root of 81533765 is about 9029.6049193749. The cubic root of 81533765 is about 433.6231890447.

The spelling of 81533765 in words is "eighty-one million, five hundred thirty-three thousand, seven hundred sixty-five".