261815913 has 6 divisors (see below), whose sum is σ = 378178554. Its totient is φ = 174543936.

The previous prime is 261815903. The next prime is 261815989. The reversal of 261815913 is 319518162.

261815913 is a `hidden beast` number, since 2 + 61 + 8 + 1 + 591 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 232623504 + 29192409 = 15252^2 + 5403^2 .

It is a de Polignac number, because none of the positive numbers 2^k-261815913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261815903) 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 5 ways as a sum of consecutive naturals, for example, 14545320 + ... + 14545337.

It is an arithmetic number, because the mean of its divisors is an integer number (63029759).

Almost surely, 2^261815913 is an apocalyptic number.

It is an amenable number.

261815913 is a deficient number, since it is larger than the sum of its proper divisors (116362641).

261815913 is a wasteful number, since it uses less digits than its factorization.

261815913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29090663 (or 29090660 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 261815913 is about 16180.7265906077. The cubic root of 261815913 is about 639.7328906511.

The spelling of 261815913 in words is "two hundred sixty-one million, eight hundred fifteen thousand, nine hundred thirteen".