81905288545 has 8 divisors (see below), whose sum is σ = 98312446440. Its totient is φ = 65506830720.

The previous prime is 81905288513. The next prime is 81905288593. The reversal of 81905288545 is 54588250918.

It can be written as a sum of positive squares in 4 ways, for example, as 3789510481 + 78115778064 = 61559^2 + 279492^2 .

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

It is not a de Polignac number, because 81905288545 - 2⁵ = 81905288513 is a prime.

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, 2154286 + ... + 2191975.

It is an arithmetic number, because the mean of its divisors is an integer number (12289055805).

Almost surely, 2^81905288545 is an apocalyptic number.

It is an amenable number.

81905288545 is a deficient number, since it is larger than the sum of its proper divisors (16407157895).

81905288545 is a wasteful number, since it uses less digits than its factorization.

81905288545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4350035.

The product of its (nonzero) digits is 4608000, while the sum is 55.

The spelling of 81905288545 in words is "eighty-one billion, nine hundred five million, two hundred eighty-eight thousand, five hundred forty-five".