81223509 has 4 divisors (see below), whose sum is σ = 108298016. Its totient is φ = 54149004.

The previous prime is 81223489. The next prime is 81223531. The reversal of 81223509 is 90532218.

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 not a de Polignac number, because 81223509 - 2⁸ = 81223253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81228509) 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, 13537249 + ... + 13537254.

It is an arithmetic number, because the mean of its divisors is an integer number (27074504).

Almost surely, 2^81223509 is an apocalyptic number.

It is an amenable number.

81223509 is a deficient number, since it is larger than the sum of its proper divisors (27074507).

81223509 is a wasteful number, since it uses less digits than its factorization.

81223509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27074506.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 81223509 is about 9012.4086125741. The cubic root of 81223509 is about 433.0724756765.

The spelling of 81223509 in words is "eighty-one million, two hundred twenty-three thousand, five hundred nine".