261534542891 has 2 divisors, whose sum is σ = 261534542892. Its totient is φ = 261534542890.

The previous prime is 261534542873. The next prime is 261534542923. The reversal of 261534542891 is 198245435162.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261534542891 is a prime.

It is not a weakly prime, because it can be changed into another prime (261534542861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130767271445 + 130767271446.

It is an arithmetic number, because the mean of its divisors is an integer number (130767271446).

Almost surely, 2^261534542891 is an apocalyptic number.

261534542891 is a deficient number, since it is larger than the sum of its proper divisors (1).

261534542891 is an equidigital number, since it uses as much as digits as its factorization.

261534542891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2073600, while the sum is 50.

The spelling of 261534542891 in words is "two hundred sixty-one billion, five hundred thirty-four million, five hundred forty-two thousand, eight hundred ninety-one".