81445305761 has 4 divisors (see below), whose sum is σ = 81619707312. Its totient is φ = 81270904212.

The previous prime is 81445305757. The next prime is 81445305787. The reversal of 81445305761 is 16750354418.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81445305761 - 2² = 81445305757 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81445305961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 87200075 + ... + 87201008.

It is an arithmetic number, because the mean of its divisors is an integer number (20404926828).

Almost surely, 2^81445305761 is an apocalyptic number.

It is an amenable number.

81445305761 is a deficient number, since it is larger than the sum of its proper divisors (174401551).

81445305761 is a wasteful number, since it uses less digits than its factorization.

81445305761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174401550.

The product of its (nonzero) digits is 403200, while the sum is 44.

The spelling of 81445305761 in words is "eighty-one billion, four hundred forty-five million, three hundred five thousand, seven hundred sixty-one".