81604071 has 8 divisors (see below), whose sum is σ = 120894960. Its totient is φ = 54402696.

The previous prime is 81604051. The next prime is 81604073. The reversal of 81604071 is 17040618.

It is a happy number.

It is not a de Polignac number, because 81604071 - 2⁶ = 81604007 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 3022373 = 81604071 / (8 + 1 + 6 + 0 + 4 + 0 + 7 + 1).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81604073) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1511160 + ... + 1511213.

It is an arithmetic number, because the mean of its divisors is an integer number (15111870).

Almost surely, 2^81604071 is an apocalyptic number.

81604071 is a deficient number, since it is larger than the sum of its proper divisors (39290889).

81604071 is a wasteful number, since it uses less digits than its factorization.

81604071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3022382 (or 3022376 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 81604071 is about 9033.4971633360. The cubic root of 81604071 is about 433.7477899934.

Adding to 81604071 its reverse (17040618), we get a palindrome (98644689).

The spelling of 81604071 in words is "eighty-one million, six hundred four thousand, seventy-one".