1261438609 has 4 divisors (see below), whose sum is σ = 1261892404. Its totient is φ = 1260984816.

The previous prime is 1261438603. The next prime is 1261438621. The reversal of 1261438609 is 9068341621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9068341621 = 4793 ⋅1891997.

It can be written as a sum of positive squares in 2 ways, for example, as 500506384 + 760932225 = 22372^2 + 27585^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261438609 - 2¹⁹ = 1260914321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1261438603) 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, 222702 + ... + 228295.

It is an arithmetic number, because the mean of its divisors is an integer number (315473101).

Almost surely, 2^1261438609 is an apocalyptic number.

It is an amenable number.

1261438609 is a deficient number, since it is larger than the sum of its proper divisors (453795).

1261438609 is an equidigital number, since it uses as much as digits as its factorization.

1261438609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 453794.

The product of its (nonzero) digits is 62208, while the sum is 40.

The square root of 1261438609 is about 35516.7370263655. The cubic root of 1261438609 is about 1080.4932043748.

The spelling of 1261438609 in words is "one billion, two hundred sixty-one million, four hundred thirty-eight thousand, six hundred nine".