81861259057 has 4 divisors (see below), whose sum is σ = 84073725556. Its totient is φ = 79648792560.

The previous prime is 81861259031. The next prime is 81861259069. The reversal of 81861259057 is 75095216818.

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 33463019041 + 48398240016 = 182929^2 + 219996^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81861259057 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81861258995 and 81861259013.

It is not an unprimeable number, because it can be changed into a prime (81861259957) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1106233194 + ... + 1106233267.

It is an arithmetic number, because the mean of its divisors is an integer number (21018431389).

Almost surely, 2^81861259057 is an apocalyptic number.

It is an amenable number.

81861259057 is a deficient number, since it is larger than the sum of its proper divisors (2212466499).

81861259057 is a wasteful number, since it uses less digits than its factorization.

81861259057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2212466498.

The product of its (nonzero) digits is 1209600, while the sum is 52.

The spelling of 81861259057 in words is "eighty-one billion, eight hundred sixty-one million, two hundred fifty-nine thousand, fifty-seven".