81949513 has 2 divisors, whose sum is σ = 81949514. Its totient is φ = 81949512.

The previous prime is 81949507. The next prime is 81949519. The reversal of 81949513 is 31594918.

It is a balanced prime because it is at equal distance from previous prime (81949507) and next prime (81949519).

It can be written as a sum of positive squares in only one way, i.e., 48274704 + 33674809 = 6948^2 + 5803^2 .

It is a cyclic number.

It is not a de Polignac number, because 81949513 - 2⁹ = 81949001 is a prime.

It is not a weakly prime, because it can be changed into another prime (81949519) 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, 40974756 + 40974757.

It is an arithmetic number, because the mean of its divisors is an integer number (40974757).

Almost surely, 2^81949513 is an apocalyptic number.

It is an amenable number.

81949513 is a deficient number, since it is larger than the sum of its proper divisors (1).

81949513 is an equidigital number, since it uses as much as digits as its factorization.

81949513 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38880, while the sum is 40.

The square root of 81949513 is about 9052.5970306868. The cubic root of 81949513 is about 434.3589677363.

The spelling of 81949513 in words is "eighty-one million, nine hundred forty-nine thousand, five hundred thirteen".