81377993 has 2 divisors, whose sum is σ = 81377994. Its totient is φ = 81377992.

The previous prime is 81377987. The next prime is 81378013. The reversal of 81377993 is 39977318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63170704 + 18207289 = 7948^2 + 4267^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81377993 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81377953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40688996 + 40688997.

It is an arithmetic number, because the mean of its divisors is an integer number (40688997).

Almost surely, 2^81377993 is an apocalyptic number.

It is an amenable number.

81377993 is a deficient number, since it is larger than the sum of its proper divisors (1).

81377993 is an equidigital number, since it uses as much as digits as its factorization.

81377993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 285768, while the sum is 47.

The square root of 81377993 is about 9020.9751690158. The cubic root of 81377993 is about 433.3468642060.

The spelling of 81377993 in words is "eighty-one million, three hundred seventy-seven thousand, nine hundred ninety-three".