81664777 has 4 divisors (see below), whose sum is σ = 81694080. Its totient is φ = 81635476.

The previous prime is 81664771. The next prime is 81664799. The reversal of 81664777 is 77746618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 77746618 = 2 ⋅38873309.

It is a cyclic number.

It is not a de Polignac number, because 81664777 - 2³ = 81664769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81664771) 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 in 3 ways as a sum of consecutive naturals, for example, 9973 + ... + 16210.

It is an arithmetic number, because the mean of its divisors is an integer number (20423520).

Almost surely, 2^81664777 is an apocalyptic number.

It is an amenable number.

81664777 is a deficient number, since it is larger than the sum of its proper divisors (29303).

81664777 is a wasteful number, since it uses less digits than its factorization.

81664777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29302.

The product of its digits is 395136, while the sum is 46.

The square root of 81664777 is about 9036.8565884383. The cubic root of 81664777 is about 433.8553196235.

The spelling of 81664777 in words is "eighty-one million, six hundred sixty-four thousand, seven hundred seventy-seven".