81477749 has 2 divisors, whose sum is σ = 81477750. Its totient is φ = 81477748.

The previous prime is 81477731. The next prime is 81477779. The reversal of 81477749 is 94777418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 79834225 + 1643524 = 8935^2 + 1282^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81477749 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81477779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40738874 + 40738875.

It is an arithmetic number, because the mean of its divisors is an integer number (40738875).

Almost surely, 2^81477749 is an apocalyptic number.

It is an amenable number.

81477749 is a deficient number, since it is larger than the sum of its proper divisors (1).

81477749 is an equidigital number, since it uses as much as digits as its factorization.

81477749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 395136, while the sum is 47.

The square root of 81477749 is about 9026.5025895969. The cubic root of 81477749 is about 433.5238625007.

The spelling of 81477749 in words is "eighty-one million, four hundred seventy-seven thousand, seven hundred forty-nine".