31389209 has 8 divisors (see below), whose sum is σ = 32372808. Its totient is φ = 30412800.

The previous prime is 31389187. The next prime is 31389221. The reversal of 31389209 is 90298313.

It can be written as a sum of positive squares in 4 ways, for example, as 15960025 + 15429184 = 3995^2 + 3928^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31389209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31389289) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7859 + ... + 11159.

It is an arithmetic number, because the mean of its divisors is an integer number (4046601).

Almost surely, 2^31389209 is an apocalyptic number.

It is an amenable number.

31389209 is a deficient number, since it is larger than the sum of its proper divisors (983599).

31389209 is a wasteful number, since it uses less digits than its factorization.

31389209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3595.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 31389209 is about 5602.6073394447. The cubic root of 31389209 is about 315.4472826142.

The spelling of 31389209 in words is "thirty-one million, three hundred eighty-nine thousand, two hundred nine".