81004661 has 2 divisors, whose sum is σ = 81004662. Its totient is φ = 81004660.

The previous prime is 81004633. The next prime is 81004663. The reversal of 81004661 is 16640018.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79299025 + 1705636 = 8905^2 + 1306^2 .

It is a cyclic number.

It is not a de Polignac number, because 81004661 - 2¹⁸ = 80742517 is a prime.

Together with 81004663, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81004661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81004663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40502330 + 40502331.

It is an arithmetic number, because the mean of its divisors is an integer number (40502331).

Almost surely, 2^81004661 is an apocalyptic number.

It is an amenable number.

81004661 is a deficient number, since it is larger than the sum of its proper divisors (1).

81004661 is an equidigital number, since it uses as much as digits as its factorization.

81004661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 81004661 is about 9000.2589407194. The cubic root of 81004661 is about 432.6831701000.

Adding to 81004661 its reverse (16640018), we get a palindrome (97644679).

The spelling of 81004661 in words is "eighty-one million, four thousand, six hundred sixty-one".