81245911805 has 8 divisors (see below), whose sum is σ = 99873023544. Its totient is φ = 63411443200.

The previous prime is 81245911793. The next prime is 81245911823. The reversal of 81245911805 is 50811954218.

It can be written as a sum of positive squares in 4 ways, for example, as 5507569369 + 75738342436 = 74213^2 + 275206^2 .

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

It is not a de Polignac number, because 81245911805 - 2²⁶ = 81178802941 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 198160556 + ... + 198160965.

It is an arithmetic number, because the mean of its divisors is an integer number (12484127943).

Almost surely, 2^81245911805 is an apocalyptic number.

It is an amenable number.

81245911805 is a deficient number, since it is larger than the sum of its proper divisors (18627111739).

81245911805 is a wasteful number, since it uses less digits than its factorization.

81245911805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396321567.

The product of its (nonzero) digits is 115200, while the sum is 44.

The spelling of 81245911805 in words is "eighty-one billion, two hundred forty-five million, nine hundred eleven thousand, eight hundred five".