81568781 has 12 divisors (see below), whose sum is σ = 97948800. Its totient is φ = 67659480.

The previous prime is 81568763. The next prime is 81568801. The reversal of 81568781 is 18786518.

It is not a de Polignac number, because 81568781 - 2¹⁰ = 81567757 is a prime.

It is a super-2 number, since 2×81568781² = 13306932067651922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81568181) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25331 + ... + 28368.

It is an arithmetic number, because the mean of its divisors is an integer number (8162400).

Almost surely, 2^81568781 is an apocalyptic number.

It is an amenable number.

81568781 is a deficient number, since it is larger than the sum of its proper divisors (16380019).

81568781 is a wasteful number, since it uses less digits than its factorization.

81568781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53744 (or 53737 counting only the distinct ones).

The product of its digits is 107520, while the sum is 44.

The square root of 81568781 is about 9031.5436665057. The cubic root of 81568781 is about 433.6852556681.

It can be divided in two parts, 815 and 68781, that added together give a palindrome (69596).

The spelling of 81568781 in words is "eighty-one million, five hundred sixty-eight thousand, seven hundred eighty-one".