81286616618 has 4 divisors (see below), whose sum is σ = 121929924930. Its totient is φ = 40643308308.

The previous prime is 81286616599. The next prime is 81286616623. The reversal of 81286616618 is 81661668218.

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

It can be written as a sum of positive squares in only one way, i.e., 78515962849 + 2770653769 = 280207^2 + 52637^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81286616618.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 20321654153 + ... + 20321654156.

Almost surely, 2^81286616618 is an apocalyptic number.

81286616618 is a deficient number, since it is larger than the sum of its proper divisors (40643308312).

81286616618 is a wasteful number, since it uses less digits than its factorization.

81286616618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40643308311.

The product of its digits is 1327104, while the sum is 53.

The spelling of 81286616618 in words is "eighty-one billion, two hundred eighty-six million, six hundred sixteen thousand, six hundred eighteen".