81775849 has 3 divisors (see below), whose sum is σ = 81784893. Its totient is φ = 81766806.

The previous prime is 81775801. The next prime is 81775871. The reversal of 81775849 is 94857718.

The square root of 81775849 is 9043.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 94857718 = 2 ⋅47428859.

It is not a de Polignac number, because 81775849 - 2¹⁹ = 81251561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81773849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 4522 + ... + 13564.

It is an arithmetic number, because the mean of its divisors is an integer number (27261631).

Almost surely, 2^81775849 is an apocalyptic number.

81775849 is the 9043-rd square number.

81775849 is the 4522-nd centered octagonal number.

It is an amenable number.

81775849 is a deficient number, since it is larger than the sum of its proper divisors (9044).

81775849 is an frugal number, since it uses more digits than its factorization.

81775849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18086 (or 9043 counting only the distinct ones).

The product of its digits is 564480, while the sum is 49.

The cubic root of 81775849 is about 434.0519255901.

Multiplying 81775849 by its sum of digits (49), we get a square (4007016601 = 63301²).

The spelling of 81775849 in words is "eighty-one million, seven hundred seventy-five thousand, eight hundred forty-nine".