261778739 has 2 divisors, whose sum is σ = 261778740. Its totient is φ = 261778738.

The previous prime is 261778697. The next prime is 261778747. The reversal of 261778739 is 937877162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261778739 - 2²⁰ = 260730163 is a prime.

It is not a weakly prime, because it can be changed into another prime (261774739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130889369 + 130889370.

It is an arithmetic number, because the mean of its divisors is an integer number (130889370).

Almost surely, 2^261778739 is an apocalyptic number.

261778739 is a deficient number, since it is larger than the sum of its proper divisors (1).

261778739 is an equidigital number, since it uses as much as digits as its factorization.

261778739 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 889056, while the sum is 50.

The square root of 261778739 is about 16179.5778375086. The cubic root of 261778739 is about 639.7026116714.

The spelling of 261778739 in words is "two hundred sixty-one million, seven hundred seventy-eight thousand, seven hundred thirty-nine".