31720109 has 4 divisors (see below), whose sum is σ = 31755840. Its totient is φ = 31684380.

The previous prime is 31720103. The next prime is 31720121. The reversal of 31720109 is 90102713.

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: 90102713 = 47 ⋅1917079.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31720109 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31720103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16499 + ... + 18320.

It is an arithmetic number, because the mean of its divisors is an integer number (7938960).

Almost surely, 2^31720109 is an apocalyptic number.

It is an amenable number.

31720109 is a deficient number, since it is larger than the sum of its proper divisors (35731).

31720109 is an equidigital number, since it uses as much as digits as its factorization.

31720109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35730.

The product of its (nonzero) digits is 378, while the sum is 23.

The square root of 31720109 is about 5632.0608128819. The cubic root of 31720109 is about 316.5518750444.

The spelling of 31720109 in words is "thirty-one million, seven hundred twenty thousand, one hundred nine".