261780197 has 12 divisors (see below), whose sum is σ = 310268556. Its totient is φ = 220147200.

The previous prime is 261780193. The next prime is 261780209. The reversal of 261780197 is 791087162.

It can be written as a sum of positive squares in 2 ways, for example, as 62236321 + 199543876 = 7889^2 + 14126^2 .

It is not a de Polignac number, because 261780197 - 2² = 261780193 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261780191) 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 in 11 ways as a sum of consecutive naturals, for example, 47804 + ... + 52997.

It is an arithmetic number, because the mean of its divisors is an integer number (25855713).

Almost surely, 2^261780197 is an apocalyptic number.

It is an amenable number.

261780197 is a deficient number, since it is larger than the sum of its proper divisors (48488359).

261780197 is a wasteful number, since it uses less digits than its factorization.

261780197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100868 (or 100861 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 41.

The square root of 261780197 is about 16179.6228942457. The cubic root of 261780197 is about 639.7037992961.

The spelling of 261780197 in words is "two hundred sixty-one million, seven hundred eighty thousand, one hundred ninety-seven".