81555309 has 32 divisors (see below), whose sum is σ = 137548800. Its totient is φ = 47274480.

The previous prime is 81555283. The next prime is 81555311. The reversal of 81555309 is 90355518.

It is a happy number.

It is not a de Polignac number, because 81555309 - 2¹¹ = 81553261 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81555329) 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 31 ways as a sum of consecutive naturals, for example, 862 + ... + 12800.

It is an arithmetic number, because the mean of its divisors is an integer number (4298400).

Almost surely, 2^81555309 is an apocalyptic number.

It is an amenable number.

81555309 is a deficient number, since it is larger than the sum of its proper divisors (55993491).

81555309 is a wasteful number, since it uses less digits than its factorization.

81555309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11982 (or 11976 counting only the distinct ones).

The product of its (nonzero) digits is 27000, while the sum is 36.

The square root of 81555309 is about 9030.7978052883. The cubic root of 81555309 is about 433.6613783571.

The spelling of 81555309 in words is "eighty-one million, five hundred fifty-five thousand, three hundred nine".