261340988957 has 2 divisors, whose sum is σ = 261340988958. Its totient is φ = 261340988956.

The previous prime is 261340988897. The next prime is 261340988971. The reversal of 261340988957 is 759889043162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 259645278916 + 1695710041 = 509554^2 + 41179^2 .

It is a cyclic number.

It is not a de Polignac number, because 261340988957 - 2¹⁸ = 261340726813 is a prime.

It is a super-2 number, since 2×261340988957² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 261340988957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261340988057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130670494478 + 130670494479.

It is an arithmetic number, because the mean of its divisors is an integer number (130670494479).

It is a 1-persistent number, because it is pandigital, but 2⋅261340988957 = 522681977914 is not.

Almost surely, 2^261340988957 is an apocalyptic number.

It is an amenable number.

261340988957 is a deficient number, since it is larger than the sum of its proper divisors (1).

261340988957 is an equidigital number, since it uses as much as digits as its factorization.

261340988957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26127360, while the sum is 62.

The spelling of 261340988957 in words is "two hundred sixty-one billion, three hundred forty million, nine hundred eighty-eight thousand, nine hundred fifty-seven".