1265721855 has 16 divisors (see below), whose sum is σ = 2113205760. Its totient is φ = 645701408.

The previous prime is 1265721851. The next prime is 1265721881. The reversal of 1265721855 is 5581275621.

It is a cyclic number.

It is not a de Polignac number, because 1265721855 - 2² = 1265721851 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265721851) 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 15 ways as a sum of consecutive naturals, for example, 1834035 + ... + 1834724.

It is an arithmetic number, because the mean of its divisors is an integer number (132075360).

Almost surely, 2^1265721855 is an apocalyptic number.

1265721855 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1265721855 is a deficient number, since it is larger than the sum of its proper divisors (847483905).

1265721855 is a wasteful number, since it uses less digits than its factorization.

1265721855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3668790.

The product of its digits is 168000, while the sum is 42.

The square root of 1265721855 is about 35576.9849059754. The cubic root of 1265721855 is about 1081.7147699318.

The spelling of 1265721855 in words is "one billion, two hundred sixty-five million, seven hundred twenty-one thousand, eight hundred fifty-five".