81107321 has 2 divisors, whose sum is σ = 81107322. Its totient is φ = 81107320.

The previous prime is 81107297. The next prime is 81107339. The reversal of 81107321 is 12370118.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63425296 + 17682025 = 7964^2 + 4205^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81107321 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81107921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40553660 + 40553661.

It is an arithmetic number, because the mean of its divisors is an integer number (40553661).

Almost surely, 2^81107321 is an apocalyptic number.

It is an amenable number.

81107321 is a deficient number, since it is larger than the sum of its proper divisors (1).

81107321 is an equidigital number, since it uses as much as digits as its factorization.

81107321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 81107321 is about 9005.9603041541. The cubic root of 81107321 is about 432.8658777048.

Adding to 81107321 its reverse (12370118), we get a palindrome (93477439).

The spelling of 81107321 in words is "eighty-one million, one hundred seven thousand, three hundred twenty-one".