81555473 has 4 divisors (see below), whose sum is σ = 81845988. Its totient is φ = 81264960.

The previous prime is 81555469. The next prime is 81555497. The reversal of 81555473 is 37455518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 37455518 = 2 ⋅18727759.

It can be written as a sum of positive squares in 2 ways, for example, as 62615569 + 18939904 = 7913^2 + 4352^2 .

It is a cyclic number.

It is not a de Polignac number, because 81555473 - 2² = 81555469 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81555403) 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 in 3 ways as a sum of consecutive naturals, for example, 144836 + ... + 145397.

It is an arithmetic number, because the mean of its divisors is an integer number (20461497).

Almost surely, 2^81555473 is an apocalyptic number.

It is an amenable number.

81555473 is a deficient number, since it is larger than the sum of its proper divisors (290515).

81555473 is a wasteful number, since it uses less digits than its factorization.

81555473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290514.

The product of its digits is 84000, while the sum is 38.

The square root of 81555473 is about 9030.8068853231. The cubic root of 81555473 is about 433.6616690409.

It can be divided in two parts, 81555 and 473, that added together give a palindrome (82028).

The spelling of 81555473 in words is "eighty-one million, five hundred fifty-five thousand, four hundred seventy-three".