81789665 has 8 divisors (see below), whose sum is σ = 99250920. Its totient is φ = 64696192.

The previous prime is 81789637. The next prime is 81789671. The reversal of 81789665 is 56698718.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1669264 + 80120401 = 1292^2 + 8951^2 .

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 81789665 - 2²⁴ = 65012449 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 91454 + ... + 92343.

It is an arithmetic number, because the mean of its divisors is an integer number (12406365).

Almost surely, 2^81789665 is an apocalyptic number.

It is an amenable number.

81789665 is a deficient number, since it is larger than the sum of its proper divisors (17461255).

81789665 is a wasteful number, since it uses less digits than its factorization.

81789665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 183891.

The product of its digits is 725760, while the sum is 50.

The square root of 81789665 is about 9043.7638735208. The cubic root of 81789665 is about 434.0763685186.

The spelling of 81789665 in words is "eighty-one million, seven hundred eighty-nine thousand, six hundred sixty-five".