31309 has 4 divisors (see below), whose sum is σ = 31680.
Its totient is φ = 30940.
The previous prime is 31307. The next prime is 31319. The reversal of 31309 is 90313.
It is a happy number.
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 a brilliant number, because the two primes have the same length.
It is a cyclic number.
It is not a de Polignac number, because 31309 - 21 = 31307 is a prime.
It is a Duffinian number.
It is a plaindrome in base 13.
It is a junction number, because it is equal to n+sod(n) for n = 31292 and 31301.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (31307) 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, 12 + ... + 250.
It is an arithmetic number, because the mean of its divisors is an integer number (7920).
231309 is an apocalyptic number.
It is an amenable number.
31309 is a deficient number, since it is larger than the sum of its proper divisors (371).
31309 is a wasteful number, since it uses less digits than its factorization.
31309 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 370.
The product of its (nonzero) digits is 81, while the sum is 16.
The square root of 31309 is about 176.9434938052.
The cubic root of 31309 is about 31.5178365432.
The spelling of 31309 in words is "thirty-one thousand, three hundred nine".