81070681 has 4 divisors (see below), whose sum is σ = 81098164. Its totient is φ = 81043200.

The previous prime is 81070679. The next prime is 81070697. The reversal of 81070681 is 18607018.

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 42133081 + 38937600 = 6491^2 + 6240^2 .

It is a cyclic number.

It is not a de Polignac number, because 81070681 - 2¹ = 81070679 is a prime.

It is a super-2 number, since 2×81070681² = 13144910635607522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81070601) 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, 8700 + ... + 15421.

It is an arithmetic number, because the mean of its divisors is an integer number (20274541).

Almost surely, 2^81070681 is an apocalyptic number.

It is an amenable number.

81070681 is a deficient number, since it is larger than the sum of its proper divisors (27483).

81070681 is a wasteful number, since it uses less digits than its factorization.

81070681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27482.

The product of its (nonzero) digits is 2688, while the sum is 31.

The square root of 81070681 is about 9003.9258659765. The cubic root of 81070681 is about 432.8006859135.

Adding to 81070681 its reverse (18607018), we get a palindrome (99677699).

The spelling of 81070681 in words is "eighty-one million, seventy thousand, six hundred eighty-one".