81504785 has 4 divisors (see below), whose sum is σ = 97805748. Its totient is φ = 65203824.

The previous prime is 81504781. The next prime is 81504791. The reversal of 81504785 is 58740518.

It is a Cunningham number, because it is equal to 9028²+1.

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

It can be written as a sum of positive squares in 2 ways, for example, as 29333056 + 52171729 = 5416^2 + 7223^2 .

It is a cyclic number.

It is not a de Polignac number, because 81504785 - 2² = 81504781 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81504781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8150474 + ... + 8150483.

It is an arithmetic number, because the mean of its divisors is an integer number (24451437).

Almost surely, 2^81504785 is an apocalyptic number.

It is an amenable number.

81504785 is a deficient number, since it is larger than the sum of its proper divisors (16300963).

81504785 is a wasteful number, since it uses less digits than its factorization.

81504785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16300962.

The product of its (nonzero) digits is 44800, while the sum is 38.

The square root of 81504785 is about 9028.0000553833. Note that the first 4 decimals coincide. The cubic root of 81504785 is about 433.5718079219.

The spelling of 81504785 in words is "eighty-one million, five hundred four thousand, seven hundred eighty-five".