81673121 has 2 divisors, whose sum is σ = 81673122. Its totient is φ = 81673120.

The previous prime is 81673099. The next prime is 81673133. The reversal of 81673121 is 12137618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72063121 + 9610000 = 8489^2 + 3100^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81673121 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_4761461 and since 81673121 and 4761461 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81673181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40836560 + 40836561.

It is an arithmetic number, because the mean of its divisors is an integer number (40836561).

Almost surely, 2^81673121 is an apocalyptic number.

It is an amenable number.

81673121 is a deficient number, since it is larger than the sum of its proper divisors (1).

81673121 is an equidigital number, since it uses as much as digits as its factorization.

81673121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 29.

The square root of 81673121 is about 9037.3182416024. The cubic root of 81673121 is about 433.8700953348.

It can be divided in two parts, 816 and 73121, that added together give a palindrome (73937).

The spelling of 81673121 in words is "eighty-one million, six hundred seventy-three thousand, one hundred twenty-one".