261651859897 has 2 divisors, whose sum is σ = 261651859898. Its totient is φ = 261651859896.

The previous prime is 261651859867. The next prime is 261651859951. The reversal of 261651859897 is 798958156162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 234770289961 + 26881569936 = 484531^2 + 163956^2 .

It is a cyclic number.

It is not a de Polignac number, because 261651859897 - 2¹¹ = 261651857849 is a prime.

It is not a weakly prime, because it can be changed into another prime (261651859817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130825929948 + 130825929949.

It is an arithmetic number, because the mean of its divisors is an integer number (130825929949).

Almost surely, 2^261651859897 is an apocalyptic number.

It is an amenable number.

261651859897 is a deficient number, since it is larger than the sum of its proper divisors (1).

261651859897 is an equidigital number, since it uses as much as digits as its factorization.

261651859897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 65318400, while the sum is 67.

The spelling of 261651859897 in words is "two hundred sixty-one billion, six hundred fifty-one million, eight hundred fifty-nine thousand, eight hundred ninety-seven".