261673251821 has 2 divisors, whose sum is σ = 261673251822. Its totient is φ = 261673251820.

The previous prime is 261673251817. The next prime is 261673251869. The reversal of 261673251821 is 128152376162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 221987034025 + 39686217796 = 471155^2 + 199214^2 .

It is a cyclic number.

It is not a de Polignac number, because 261673251821 - 2² = 261673251817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261673251811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130836625910 + 130836625911.

It is an arithmetic number, because the mean of its divisors is an integer number (130836625911).

Almost surely, 2^261673251821 is an apocalyptic number.

It is an amenable number.

261673251821 is a deficient number, since it is larger than the sum of its proper divisors (1).

261673251821 is an equidigital number, since it uses as much as digits as its factorization.

261673251821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 44.

The spelling of 261673251821 in words is "two hundred sixty-one billion, six hundred seventy-three million, two hundred fifty-one thousand, eight hundred twenty-one".