81563785 has 4 divisors (see below), whose sum is σ = 97876548. Its totient is φ = 65251024.

The previous prime is 81563761. The next prime is 81563809. The reversal of 81563785 is 58736518.

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

It is an interprime number because it is at equal distance from previous prime (81563761) and next prime (81563809).

It can be written as a sum of positive squares in 2 ways, for example, as 61921161 + 19642624 = 7869^2 + 4432^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81563785 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8156374 + ... + 8156383.

It is an arithmetic number, because the mean of its divisors is an integer number (24469137).

Almost surely, 2^81563785 is an apocalyptic number.

It is an amenable number.

81563785 is a deficient number, since it is larger than the sum of its proper divisors (16312763).

81563785 is a wasteful number, since it uses less digits than its factorization.

81563785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16312762.

The product of its digits is 201600, while the sum is 43.

The square root of 81563785 is about 9031.2670761084. The cubic root of 81563785 is about 433.6764012357.

The spelling of 81563785 in words is "eighty-one million, five hundred sixty-three thousand, seven hundred eighty-five".