72309 has 4 divisors (see below), whose sum is σ = 96416. Its totient is φ = 48204.

The previous prime is 72307. The next prime is 72313. The reversal of 72309 is 90327.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90327 = 3 ⋅30109.

It is not a de Polignac number, because 72309 - 2¹ = 72307 is a prime.

It is a D-number.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72307) 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, 12049 + ... + 12054.

It is an arithmetic number, because the mean of its divisors is an integer number (24104).

2⁷²³⁰⁹ is an apocalyptic number.

It is an amenable number.

72309 is a deficient number, since it is larger than the sum of its proper divisors (24107).

72309 is a wasteful number, since it uses less digits than its factorization.

72309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24106.

The product of its (nonzero) digits is 378, while the sum is 21.

The square root of 72309 is about 268.9033283543. The cubic root of 72309 is about 41.6611050354.

The spelling of 72309 in words is "seventy-two thousand, three hundred nine".