261553251266621 has 2 divisors, whose sum is σ = 261553251266622. Its totient is φ = 261553251266620.

The previous prime is 261553251266561. The next prime is 261553251266687. The reversal of 261553251266621 is 126662152355162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 261412663764121 + 140587502500 = 16168261^2 + 374950^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261553251266621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261553251266821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130776625633310 + 130776625633311.

It is an arithmetic number, because the mean of its divisors is an integer number (130776625633311).

Almost surely, 2^{261553251266621} is an apocalyptic number.

It is an amenable number.

261553251266621 is a deficient number, since it is larger than the sum of its proper divisors (1).

261553251266621 is an equidigital number, since it uses as much as digits as its factorization.

261553251266621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776000, while the sum is 53.

The spelling of 261553251266621 in words is "two hundred sixty-one trillion, five hundred fifty-three billion, two hundred fifty-one million, two hundred sixty-six thousand, six hundred twenty-one".