1391243209 has 2 divisors, whose sum is σ = 1391243210. Its totient is φ = 1391243208.

The previous prime is 1391243197. The next prime is 1391243219. The reversal of 1391243209 is 9023421931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1372924809 + 18318400 = 37053^2 + 4280^2 .

It is an emirp because it is prime and its reverse (9023421931) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1391243209 - 2⁵ = 1391243177 is a prime.

It is not a weakly prime, because it can be changed into another prime (1391243219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 695621604 + 695621605.

It is an arithmetic number, because the mean of its divisors is an integer number (695621605).

Almost surely, 2^1391243209 is an apocalyptic number.

It is an amenable number.

1391243209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1391243209 is an equidigital number, since it uses as much as digits as its factorization.

1391243209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 34.

The square root of 1391243209 is about 37299.3727695252. The cubic root of 1391243209 is about 1116.3516513757.

It can be divided in two parts, 13912 and 43209, that added together give a square (57121 = 239²).

The spelling of 1391243209 in words is "one billion, three hundred ninety-one million, two hundred forty-three thousand, two hundred nine".