81912449 has 2 divisors, whose sum is σ = 81912450. Its totient is φ = 81912448.

The previous prime is 81912427. The next prime is 81912461. The reversal of 81912449 is 94421918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81360400 + 552049 = 9020^2 + 743^2 .

It is a cyclic number.

It is not a de Polignac number, because 81912449 - 2²⁰ = 80863873 is a prime.

It is equal to p_4774592 and since 81912449 and 4774592 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81912469) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40956224 + 40956225.

It is an arithmetic number, because the mean of its divisors is an integer number (40956225).

Almost surely, 2^81912449 is an apocalyptic number.

It is an amenable number.

81912449 is a deficient number, since it is larger than the sum of its proper divisors (1).

81912449 is an equidigital number, since it uses as much as digits as its factorization.

81912449 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 38.

The square root of 81912449 is about 9050.5496518167. The cubic root of 81912449 is about 434.2934741257.

The spelling of 81912449 in words is "eighty-one million, nine hundred twelve thousand, four hundred forty-nine".