81550811 has 4 divisors (see below), whose sum is σ = 81575592. Its totient is φ = 81526032.

The previous prime is 81550783. The next prime is 81550823. The reversal of 81550811 is 11805518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11805518 = 2 ⋅5902759.

It is a cyclic number.

It is not a de Polignac number, because 81550811 - 2²² = 77356507 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81550211) 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 3 ways as a sum of consecutive naturals, for example, 6530 + ... + 14343.

It is an arithmetic number, because the mean of its divisors is an integer number (20393898).

Almost surely, 2^81550811 is an apocalyptic number.

81550811 is a deficient number, since it is larger than the sum of its proper divisors (24781).

81550811 is a wasteful number, since it uses less digits than its factorization.

81550811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24780.

The product of its (nonzero) digits is 1600, while the sum is 29.

The square root of 81550811 is about 9030.5487651637. The cubic root of 81550811 is about 433.6534056706.

The spelling of 81550811 in words is "eighty-one million, five hundred fifty thousand, eight hundred eleven".