81415509 has 40 divisors (see below), whose sum is σ = 129070080. Its totient is φ = 45638208.

The previous prime is 81415507. The next prime is 81415511. The reversal of 81415509 is 90551418.

It is an interprime number because it is at equal distance from previous prime (81415507) and next prime (81415511).

It is not a de Polignac number, because 81415509 - 2¹ = 81415507 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81415509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81415501) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 641004 + ... + 641130.

It is an arithmetic number, because the mean of its divisors is an integer number (3226752).

Almost surely, 2^81415509 is an apocalyptic number.

81415509 is a gapful number since it is divisible by the number (89) formed by its first and last digit.

It is an amenable number.

81415509 is a deficient number, since it is larger than the sum of its proper divisors (47654571).

81415509 is an equidigital number, since it uses as much as digits as its factorization.

81415509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 226 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 33.

The square root of 81415509 is about 9023.0543054999. The cubic root of 81415509 is about 433.4134462664.

The spelling of 81415509 in words is "eighty-one million, four hundred fifteen thousand, five hundred nine".