261646776502655 has 4 divisors (see below), whose sum is σ = 313976131803192. Its totient is φ = 209317421202120.

The previous prime is 261646776502549. The next prime is 261646776502669. The reversal of 261646776502655 is 556205677646162.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 261646776502655 - 2³² = 261642481535359 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26164677650261 + ... + 26164677650270.

It is an arithmetic number, because the mean of its divisors is an integer number (78494032950798).

Almost surely, 2^{261646776502655} is an apocalyptic number.

261646776502655 is a deficient number, since it is larger than the sum of its proper divisors (52329355300537).

261646776502655 is an equidigital number, since it uses as much as digits as its factorization.

261646776502655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52329355300536.

The product of its (nonzero) digits is 762048000, while the sum is 68.

The spelling of 261646776502655 in words is "two hundred sixty-one trillion, six hundred forty-six billion, seven hundred seventy-six million, five hundred two thousand, six hundred fifty-five".