81648641 has 4 divisors (see below), whose sum is σ = 81666900. Its totient is φ = 81630384.

The previous prime is 81648607. The next prime is 81648647. The reversal of 81648641 is 14684618.

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 51782416 + 29866225 = 7196^2 + 5465^2 .

It is a cyclic number.

It is not a de Polignac number, because 81648641 - 2⁶ = 81648577 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81648595 and 81648604.

It is not an unprimeable number, because it can be changed into a prime (81648647) 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, 2615 + ... + 13043.

It is an arithmetic number, because the mean of its divisors is an integer number (20416725).

Almost surely, 2^81648641 is an apocalyptic number.

It is an amenable number.

81648641 is a deficient number, since it is larger than the sum of its proper divisors (18259).

81648641 is a wasteful number, since it uses less digits than its factorization.

81648641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18258.

The product of its digits is 36864, while the sum is 38.

The square root of 81648641 is about 9035.9637560141. The cubic root of 81648641 is about 433.8267428375.

The spelling of 81648641 in words is "eighty-one million, six hundred forty-eight thousand, six hundred forty-one".