31909 has 4 divisors (see below), whose sum is σ = 33804. Its totient is φ = 30016.

The previous prime is 31907. The next prime is 31957. The reversal of 31909 is 90913.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90913 = 229 ⋅397.

It can be written as a sum of positive squares in 2 ways, for example, as 22500 + 9409 = 150^2 + 97^2 .

It is a cyclic number.

It is not a de Polignac number, because 31909 - 2¹ = 31907 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31909.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31907) 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, 922 + ... + 955.

It is an arithmetic number, because the mean of its divisors is an integer number (8451).

2³¹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

31909 is a deficient number, since it is larger than the sum of its proper divisors (1895).

31909 is a wasteful number, since it uses less digits than its factorization.

31909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1894.

The product of its (nonzero) digits is 243, while the sum is 22.

The square root of 31909 is about 178.6309043811. The cubic root of 31909 is about 31.7178979889.

The spelling of 31909 in words is "thirty-one thousand, nine hundred nine".