81509659 has 8 divisors (see below), whose sum is σ = 101622528. Its totient is φ = 63513960.

The previous prime is 81509653. The next prime is 81509693. The reversal of 81509659 is 95690518.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81509659 - 2⁵ = 81509627 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81509653) 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 7 ways as a sum of consecutive naturals, for example, 529207 + ... + 529360.

It is an arithmetic number, because the mean of its divisors is an integer number (12702816).

Almost surely, 2^81509659 is an apocalyptic number.

81509659 is a deficient number, since it is larger than the sum of its proper divisors (20112869).

81509659 is a wasteful number, since it uses less digits than its factorization.

81509659 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1058585.

The product of its (nonzero) digits is 97200, while the sum is 43.

The square root of 81509659 is about 9028.2699893169. The cubic root of 81509659 is about 433.5804503056.

The spelling of 81509659 in words is "eighty-one million, five hundred nine thousand, six hundred fifty-nine".