81775807 has 4 divisors (see below), whose sum is σ = 83116456. Its totient is φ = 80435160.

The previous prime is 81775801. The next prime is 81775871. The reversal of 81775807 is 70857718.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 70857718 = 2 ⋅35428859.

It is a cyclic number.

It is not a de Polignac number, because 81775807 - 2¹¹ = 81773759 is a prime.

It is a super-2 number, since 2×81775807² = 13374565221002498, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81775801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 670233 + ... + 670354.

It is an arithmetic number, because the mean of its divisors is an integer number (20779114).

Almost surely, 2^81775807 is an apocalyptic number.

81775807 is a deficient number, since it is larger than the sum of its proper divisors (1340649).

81775807 is a wasteful number, since it uses less digits than its factorization.

81775807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1340648.

The product of its (nonzero) digits is 109760, while the sum is 43.

The square root of 81775807 is about 9042.9976777615. The cubic root of 81775807 is about 434.0518512805.

The spelling of 81775807 in words is "eighty-one million, seven hundred seventy-five thousand, eight hundred seven".