1261522789 has 4 divisors (see below), whose sum is σ = 1269558124. Its totient is φ = 1253487456.

The previous prime is 1261522781. The next prime is 1261522811. The reversal of 1261522789 is 9872251621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9872251621 = 43 ⋅229587247.

It can be written as a sum of positive squares in 2 ways, for example, as 339185889 + 922336900 = 18417^2 + 30370^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261522789 - 2³ = 1261522781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261522781) 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, 4017432 + ... + 4017745.

It is an arithmetic number, because the mean of its divisors is an integer number (317389531).

Almost surely, 2^1261522789 is an apocalyptic number.

It is an amenable number.

1261522789 is a deficient number, since it is larger than the sum of its proper divisors (8035335).

1261522789 is an equidigital number, since it uses as much as digits as its factorization.

1261522789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8035334.

The product of its digits is 120960, while the sum is 43.

The square root of 1261522789 is about 35517.9220816759. The cubic root of 1261522789 is about 1080.5172388103.

The spelling of 1261522789 in words is "one billion, two hundred sixty-one million, five hundred twenty-two thousand, seven hundred eighty-nine".