81605144923 has 4 divisors (see below), whose sum is σ = 81755986768. Its totient is φ = 81454303080.

The previous prime is 81605144869. The next prime is 81605144927. The reversal of 81605144923 is 32944150618.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81605144923 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81605144923.

It is not an unprimeable number, because it can be changed into a prime (81605144927) 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, 75420111 + ... + 75421192.

It is an arithmetic number, because the mean of its divisors is an integer number (20438996692).

Almost surely, 2^81605144923 is an apocalyptic number.

81605144923 is a deficient number, since it is larger than the sum of its proper divisors (150841845).

81605144923 is a wasteful number, since it uses less digits than its factorization.

81605144923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150841844.

The product of its (nonzero) digits is 207360, while the sum is 43.

The spelling of 81605144923 in words is "eighty-one billion, six hundred five million, one hundred forty-four thousand, nine hundred twenty-three".