261943209 has 12 divisors (see below), whose sum is σ = 412759152. Its totient is φ = 158753400.

The previous prime is 261943193. The next prime is 261943243. The reversal of 261943209 is 902349162.

261943209 is a `hidden beast` number, since 2 + 619 + 4 + 32 + 0 + 9 = 666.

It is not a de Polignac number, because 261943209 - 2⁴ = 261943193 is a prime.

It is a super-2 number, since 2×261943209² = 137228489482435362, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261943289) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1322847 + ... + 1323044.

It is an arithmetic number, because the mean of its divisors is an integer number (34396596).

Almost surely, 2^261943209 is an apocalyptic number.

It is an amenable number.

261943209 is a deficient number, since it is larger than the sum of its proper divisors (150815943).

261943209 is a wasteful number, since it uses less digits than its factorization.

261943209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2645908 (or 2645905 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 261943209 is about 16184.6596813155. The cubic root of 261943209 is about 639.8365541279.

It can be divided in two parts, 26194 and 3209, that added together give a triangular number (29403 = T₂₄₂).

The spelling of 261943209 in words is "two hundred sixty-one million, nine hundred forty-three thousand, two hundred nine".