81705378499 has 4 divisors (see below), whose sum is σ = 82348728064. Its totient is φ = 81062028936.

The previous prime is 81705378493. The next prime is 81705378527. The reversal of 81705378499 is 99487350718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81705378499 - 2⁵ = 81705378467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81705378493) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 321674592 + ... + 321674845.

It is an arithmetic number, because the mean of its divisors is an integer number (20587182016).

Almost surely, 2^81705378499 is an apocalyptic number.

81705378499 is a deficient number, since it is larger than the sum of its proper divisors (643349565).

81705378499 is a wasteful number, since it uses less digits than its factorization.

81705378499 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643349564.

The product of its (nonzero) digits is 15240960, while the sum is 61.

The spelling of 81705378499 in words is "eighty-one billion, seven hundred five million, three hundred seventy-eight thousand, four hundred ninety-nine".