81928609 has 8 divisors (see below), whose sum is σ = 94818560. Its totient is φ = 69335136.

The previous prime is 81928607. The next prime is 81928633. The reversal of 81928609 is 90682918.

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 81928609 - 2¹ = 81928607 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81928601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73524 + ... + 74629.

It is an arithmetic number, because the mean of its divisors is an integer number (11852320).

Almost surely, 2^81928609 is an apocalyptic number.

It is an amenable number.

81928609 is a deficient number, since it is larger than the sum of its proper divisors (12889951).

81928609 is a wasteful number, since it uses less digits than its factorization.

81928609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148239.

The product of its (nonzero) digits is 62208, while the sum is 43.

The square root of 81928609 is about 9051.4423712467. The cubic root of 81928609 is about 434.3220319382.

The spelling of 81928609 in words is "eighty-one million, nine hundred twenty-eight thousand, six hundred nine".