1261405439 has 4 divisors (see below), whose sum is σ = 1441606224. Its totient is φ = 1081204656.

The previous prime is 1261405367. The next prime is 1261405477. The reversal of 1261405439 is 9345041621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9345041621 = 20593 ⋅453797.

It is not a de Polignac number, because 1261405439 - 2¹⁶ = 1261339903 is a prime.

It is a super-2 number, since 2×1261405439² = 3182287363077565442, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1261405399 and 1261405408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261405939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 90100382 + ... + 90100395.

It is an arithmetic number, because the mean of its divisors is an integer number (360401556).

Almost surely, 2^1261405439 is an apocalyptic number.

1261405439 is a deficient number, since it is larger than the sum of its proper divisors (180200785).

1261405439 is an equidigital number, since it uses as much as digits as its factorization.

1261405439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180200784.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 1261405439 is about 35516.2700603540. The cubic root of 1261405439 is about 1080.4837336341.

The spelling of 1261405439 in words is "one billion, two hundred sixty-one million, four hundred five thousand, four hundred thirty-nine".