261045209 has 4 divisors (see below), whose sum is σ = 264190416. Its totient is φ = 257900004.

The previous prime is 261045181. The next prime is 261045221. The reversal of 261045209 is 902540162.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 902540162 = 2 ⋅451270081.

It is a cyclic number.

It is not a de Polignac number, because 261045209 - 2¹² = 261041113 is a prime.

It is a super-2 number, since 2×261045209² = 136289202283707362, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261045229) 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 3 ways as a sum of consecutive naturals, for example, 1572479 + ... + 1572644.

It is an arithmetic number, because the mean of its divisors is an integer number (66047604).

Almost surely, 2^261045209 is an apocalyptic number.

It is an amenable number.

261045209 is a deficient number, since it is larger than the sum of its proper divisors (3145207).

261045209 is an equidigital number, since it uses as much as digits as its factorization.

261045209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3145206.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 261045209 is about 16156.8935442430. The cubic root of 261045209 is about 639.1045493170.

It can be divided in two parts, 26104 and 5209, that added together give a palindrome (31313).

The spelling of 261045209 in words is "two hundred sixty-one million, forty-five thousand, two hundred nine".