81099913 has 2 divisors, whose sum is σ = 81099914. Its totient is φ = 81099912.

The previous prime is 81099859. The next prime is 81099917. The reversal of 81099913 is 31999018.

It is the 3677-th star number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69355584 + 11744329 = 8328^2 + 3427^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81099913 is a prime.

It is not a weakly prime, because it can be changed into another prime (81099917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40549956 + 40549957.

It is an arithmetic number, because the mean of its divisors is an integer number (40549957).

Almost surely, 2^81099913 is an apocalyptic number.

It is an amenable number.

81099913 is a deficient number, since it is larger than the sum of its proper divisors (1).

81099913 is an equidigital number, since it uses as much as digits as its factorization.

81099913 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17496, while the sum is 40.

The square root of 81099913 is about 9005.5490115817. The cubic root of 81099913 is about 432.8526985901.

The spelling of 81099913 in words is "eighty-one million, ninety-nine thousand, nine hundred thirteen".