81329609 has 4 divisors (see below), whose sum is σ = 83313300. Its totient is φ = 79345920.

The previous prime is 81329597. The next prime is 81329623. The reversal of 81329609 is 90692318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 30250000 + 51079609 = 5500^2 + 7147^2 .

It is a cyclic number.

It is not a de Polignac number, because 81329609 - 2²⁴ = 64552393 is a prime.

It is a super-2 number, since 2×81329609² = 13229010600185762, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81329629) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 991784 + ... + 991865.

It is an arithmetic number, because the mean of its divisors is an integer number (20828325).

Almost surely, 2^81329609 is an apocalyptic number.

It is an amenable number.

81329609 is a deficient number, since it is larger than the sum of its proper divisors (1983691).

81329609 is a wasteful number, since it uses less digits than its factorization.

81329609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1983690.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 81329609 is about 9018.2930203005. The cubic root of 81329609 is about 433.2609637856.

The spelling of 81329609 in words is "eighty-one million, three hundred twenty-nine thousand, six hundred nine".