81807649 has 16 divisors (see below), whose sum is σ = 103671936. Its totient is φ = 62697600.

The previous prime is 81807631. The next prime is 81807697. The reversal of 81807649 is 94670818.

It is a de Polignac number, because none of the positive numbers 2^k-81807649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81807049) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4012 + ... + 13405.

It is an arithmetic number, because the mean of its divisors is an integer number (6479496).

Almost surely, 2^81807649 is an apocalyptic number.

It is an amenable number.

81807649 is a deficient number, since it is larger than the sum of its proper divisors (21864287).

81807649 is a wasteful number, since it uses less digits than its factorization.

81807649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17496.

The product of its (nonzero) digits is 96768, while the sum is 43.

The square root of 81807649 is about 9044.7580951621. The cubic root of 81807649 is about 434.1081812475.

The spelling of 81807649 in words is "eighty-one million, eight hundred seven thousand, six hundred forty-nine".