81291620818 has 16 divisors (see below), whose sum is σ = 123412512384. Its totient is φ = 40156187760.

The previous prime is 81291620803. The next prime is 81291620849. The reversal of 81291620818 is 81802619218.

It is a happy 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, 438993 + ... + 596068.

It is an arithmetic number, because the mean of its divisors is an integer number (7713282024).

Almost surely, 2^81291620818 is an apocalyptic number.

81291620818 is a deficient number, since it is larger than the sum of its proper divisors (42120891566).

81291620818 is a wasteful number, since it uses less digits than its factorization.

81291620818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1035537.

The product of its (nonzero) digits is 110592, while the sum is 46.

The spelling of 81291620818 in words is "eighty-one billion, two hundred ninety-one million, six hundred twenty thousand, eight hundred eighteen".