261809965 has 16 divisors (see below), whose sum is σ = 326309040. Its totient is φ = 201484800.

The previous prime is 261809959. The next prime is 261809993. The reversal of 261809965 is 569908162.

It can be written as a sum of positive squares in 8 ways, for example, as 29735209 + 232074756 = 5453^2 + 15234^2 .

It is not a de Polignac number, because 261809965 - 2³ = 261809957 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8515 + ... + 24415.

It is an arithmetic number, because the mean of its divisors is an integer number (20394315).

Almost surely, 2^261809965 is an apocalyptic number.

It is an amenable number.

261809965 is a deficient number, since it is larger than the sum of its proper divisors (64499075).

261809965 is a wasteful number, since it uses less digits than its factorization.

261809965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16032.

The product of its (nonzero) digits is 233280, while the sum is 46.

The square root of 261809965 is about 16180.5427906483. The cubic root of 261809965 is about 639.7280460766.

The spelling of 261809965 in words is "two hundred sixty-one million, eight hundred nine thousand, nine hundred sixty-five".