81812553 has 4 divisors (see below), whose sum is σ = 109083408. Its totient is φ = 54541700.

The previous prime is 81812501. The next prime is 81812557. The reversal of 81812553 is 35521818.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 81812553 - 2¹⁸ = 81550409 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81812557) 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, 13635423 + ... + 13635428.

It is an arithmetic number, because the mean of its divisors is an integer number (27270852).

Almost surely, 2^81812553 is an apocalyptic number.

It is an amenable number.

81812553 is a deficient number, since it is larger than the sum of its proper divisors (27270855).

81812553 is a wasteful number, since it uses less digits than its factorization.

81812553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27270854.

The product of its digits is 9600, while the sum is 33.

The square root of 81812553 is about 9045.0291873493. The cubic root of 81812553 is about 434.1168553508.

The spelling of 81812553 in words is "eighty-one million, eight hundred twelve thousand, five hundred fifty-three".