1261555361 has 8 divisors (see below), whose sum is σ = 1423699200. Its totient is φ = 1107321040.

The previous prime is 1261555349. The next prime is 1261555387. The reversal of 1261555361 is 1635551621.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1261555361 - 2¹⁴ = 1261538977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1261557361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1977041 + ... + 1977678.

It is an arithmetic number, because the mean of its divisors is an integer number (177962400).

Almost surely, 2^1261555361 is an apocalyptic number.

1261555361 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1261555361 is a deficient number, since it is larger than the sum of its proper divisors (162143839).

1261555361 is a wasteful number, since it uses less digits than its factorization.

1261555361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3954759.

The product of its digits is 27000, while the sum is 35.

The square root of 1261555361 is about 35518.3806077924. The cubic root of 1261555361 is about 1080.5265382340.

It can be divided in two parts, 12615 and 55361, that added together give a palindrome (67976).

The spelling of 1261555361 in words is "one billion, two hundred sixty-one million, five hundred fifty-five thousand, three hundred sixty-one".