81133309 has 2 divisors, whose sum is σ = 81133310. Its totient is φ = 81133308.

The previous prime is 81133289. The next prime is 81133321. The reversal of 81133309 is 90333118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60793209 + 20340100 = 7797^2 + 4510^2 .

It is a cyclic number.

It is not a de Polignac number, because 81133309 - 2⁵ = 81133277 is a prime.

It is a super-2 number, since 2×81133309² = 13165227658578962, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81133399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40566654 + 40566655.

It is an arithmetic number, because the mean of its divisors is an integer number (40566655).

Almost surely, 2^81133309 is an apocalyptic number.

It is an amenable number.

81133309 is a deficient number, since it is larger than the sum of its proper divisors (1).

81133309 is an equidigital number, since it uses as much as digits as its factorization.

81133309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 81133309 is about 9007.4030108572. The cubic root of 81133309 is about 432.9121050039.

The spelling of 81133309 in words is "eighty-one million, one hundred thirty-three thousand, three hundred nine".