131217209 has 4 divisors (see below), whose sum is σ = 134268816. Its totient is φ = 128165604.

The previous prime is 131217197. The next prime is 131217223. The reversal of 131217209 is 902712131.

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: 902712131 = 11593 ⋅77867.

It is a cyclic number.

It is not a de Polignac number, because 131217209 - 2²⁴ = 114439993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (131217259) 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, 1525739 + ... + 1525824.

It is an arithmetic number, because the mean of its divisors is an integer number (33567204).

Almost surely, 2^131217209 is an apocalyptic number.

It is an amenable number.

131217209 is a deficient number, since it is larger than the sum of its proper divisors (3051607).

131217209 is an equidigital number, since it uses as much as digits as its factorization.

131217209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3051606.

The product of its (nonzero) digits is 756, while the sum is 26.

The square root of 131217209 is about 11455.0080314245. The cubic root of 131217209 is about 508.1558527834.

The spelling of 131217209 in words is "one hundred thirty-one million, two hundred seventeen thousand, two hundred nine".