81899619745 has 4 divisors (see below), whose sum is σ = 98279543700. Its totient is φ = 65519695792.

The previous prime is 81899619733. The next prime is 81899619761. The reversal of 81899619745 is 54791699818.

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

It can be written as a sum of positive squares in 2 ways, for example, as 39183410704 + 42716209041 = 197948^2 + 206679^2 .

It is a cyclic number.

It is not a de Polignac number, because 81899619745 - 2³³ = 73309685153 is a prime.

It is a Smith number, since the sum of its digits (67) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8189961970 + ... + 8189961979.

It is an arithmetic number, because the mean of its divisors is an integer number (24569885925).

Almost surely, 2^81899619745 is an apocalyptic number.

It is an amenable number.

81899619745 is a deficient number, since it is larger than the sum of its proper divisors (16379923955).

81899619745 is a wasteful number, since it uses less digits than its factorization.

81899619745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16379923954.

The product of its digits is 39191040, while the sum is 67.

The spelling of 81899619745 in words is "eighty-one billion, eight hundred ninety-nine million, six hundred nineteen thousand, seven hundred forty-five".