263644987561 has 2 divisors, whose sum is σ = 263644987562. Its totient is φ = 263644987560.

The previous prime is 263644987537. The next prime is 263644987657. The reversal of 263644987561 is 165789446362.

263644987561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 215789049961 + 47855937600 = 464531^2 + 218760^2 .

It is a cyclic number.

It is not a de Polignac number, because 263644987561 - 2⁷ = 263644987433 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 263644987561.

It is not a weakly prime, because it can be changed into another prime (263644987861) 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 as a sum of consecutive naturals, namely, 131822493780 + 131822493781.

It is an arithmetic number, because the mean of its divisors is an integer number (131822493781).

Almost surely, 2^263644987561 is an apocalyptic number.

It is an amenable number.

263644987561 is a deficient number, since it is larger than the sum of its proper divisors (1).

263644987561 is an equidigital number, since it uses as much as digits as its factorization.

263644987561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52254720, while the sum is 61.

The spelling of 263644987561 in words is "two hundred sixty-three billion, six hundred forty-four million, nine hundred eighty-seven thousand, five hundred sixty-one".