81209640778 has 8 divisors (see below), whose sum is σ = 139216527072. Its totient is φ = 34804131756.

The previous prime is 81209640773. The next prime is 81209640779. The reversal of 81209640778 is 87704690218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (81209640773) 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, 2900344300 + ... + 2900344327.

It is an arithmetic number, because the mean of its divisors is an integer number (17402065884).

Almost surely, 2^81209640778 is an apocalyptic number.

81209640778 is a deficient number, since it is larger than the sum of its proper divisors (58006886294).

81209640778 is a wasteful number, since it uses less digits than its factorization.

81209640778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5800688636.

The product of its (nonzero) digits is 1354752, while the sum is 52.

The spelling of 81209640778 in words is "eighty-one billion, two hundred nine million, six hundred forty thousand, seven hundred seventy-eight".