81138073 has 2 divisors, whose sum is σ = 81138074. Its totient is φ = 81138072.

The previous prime is 81138049. The next prime is 81138091. The reversal of 81138073 is 37083118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66145689 + 14992384 = 8133^2 + 3872^2 .

It is a cyclic number.

It is not a de Polignac number, because 81138073 - 2⁹ = 81137561 is a prime.

It is not a weakly prime, because it can be changed into another prime (81138023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40569036 + 40569037.

It is an arithmetic number, because the mean of its divisors is an integer number (40569037).

Almost surely, 2^81138073 is an apocalyptic number.

It is an amenable number.

81138073 is a deficient number, since it is larger than the sum of its proper divisors (1).

81138073 is an equidigital number, since it uses as much as digits as its factorization.

81138073 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 81138073 is about 9007.6674561176. The cubic root of 81138073 is about 432.9205781079.

The spelling of 81138073 in words is "eighty-one million, one hundred thirty-eight thousand, seventy-three".