261561209 has 8 divisors (see below), whose sum is σ = 321921600. Its totient is φ = 206949456.

The previous prime is 261561197. The next prime is 261561227. The reversal of 261561209 is 902165162.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261561209 - 2⁴ = 261561193 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261561259) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1437059 + ... + 1437240.

It is an arithmetic number, because the mean of its divisors is an integer number (40240200).

Almost surely, 2^261561209 is an apocalyptic number.

It is an amenable number.

261561209 is a deficient number, since it is larger than the sum of its proper divisors (60360391).

261561209 is a wasteful number, since it uses less digits than its factorization.

261561209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2874319.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 261561209 is about 16172.8540771257. The cubic root of 261561209 is about 639.5253715693.

The spelling of 261561209 in words is "two hundred sixty-one million, five hundred sixty-one thousand, two hundred nine".