261399057991 has 2 divisors, whose sum is σ = 261399057992. Its totient is φ = 261399057990.

The previous prime is 261399057971. The next prime is 261399058001. The reversal of 261399057991 is 199750993162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261399057991 - 2¹¹ = 261399055943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261399057971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130699528995 + 130699528996.

It is an arithmetic number, because the mean of its divisors is an integer number (130699528996).

Almost surely, 2^261399057991 is an apocalyptic number.

261399057991 is a deficient number, since it is larger than the sum of its proper divisors (1).

261399057991 is an equidigital number, since it uses as much as digits as its factorization.

261399057991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8266860, while the sum is 61.

The spelling of 261399057991 in words is "two hundred sixty-one billion, three hundred ninety-nine million, fifty-seven thousand, nine hundred ninety-one".