261401209 has 4 divisors (see below), whose sum is σ = 261788004. Its totient is φ = 261014416.

The previous prime is 261401201. The next prime is 261401243. The reversal of 261401209 is 902104162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 180311184 + 81090025 = 13428^2 + 9005^2 .

It is a cyclic number.

It is not a de Polignac number, because 261401209 - 2³ = 261401201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261401201) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 192382 + ... + 193735.

It is an arithmetic number, because the mean of its divisors is an integer number (65447001).

Almost surely, 2^261401209 is an apocalyptic number.

It is an amenable number.

261401209 is a deficient number, since it is larger than the sum of its proper divisors (386795).

261401209 is an equidigital number, since it uses as much as digits as its factorization.

261401209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386794.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 261401209 is about 16167.9067599983. The cubic root of 261401209 is about 639.3949432957.

The spelling of 261401209 in words is "two hundred sixty-one million, four hundred one thousand, two hundred nine".