81729865 has 8 divisors (see below), whose sum is σ = 112086720. Its totient is φ = 56043312.

The previous prime is 81729841. The next prime is 81729881. The reversal of 81729865 is 56892718.

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 81729865 - 2¹⁹ = 81205577 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, 1167535 + ... + 1167604.

It is an arithmetic number, because the mean of its divisors is an integer number (14010840).

Almost surely, 2^81729865 is an apocalyptic number.

It is an amenable number.

81729865 is a deficient number, since it is larger than the sum of its proper divisors (30356855).

81729865 is a wasteful number, since it uses less digits than its factorization.

81729865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2335151.

The product of its digits is 241920, while the sum is 46.

The square root of 81729865 is about 9040.4571233981. The cubic root of 81729865 is about 433.9705519883.

The spelling of 81729865 in words is "eighty-one million, seven hundred twenty-nine thousand, eight hundred sixty-five".