261402565 has 4 divisors (see below), whose sum is σ = 313683084. Its totient is φ = 209122048.

The previous prime is 261402529. The next prime is 261402569. The reversal of 261402565 is 565204162.

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 165225316 + 96177249 = 12854^2 + 9807^2 .

It is a cyclic number.

It is not a de Polignac number, because 261402565 - 2¹³ = 261394373 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261402569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26140252 + ... + 26140261.

It is an arithmetic number, because the mean of its divisors is an integer number (78420771).

Almost surely, 2^261402565 is an apocalyptic number.

It is an amenable number.

261402565 is a deficient number, since it is larger than the sum of its proper divisors (52280519).

261402565 is an equidigital number, since it uses as much as digits as its factorization.

261402565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52280518.

The product of its (nonzero) digits is 14400, while the sum is 31.

The square root of 261402565 is about 16167.9486948716. The cubic root of 261402565 is about 639.3960488989.

The spelling of 261402565 in words is "two hundred sixty-one million, four hundred two thousand, five hundred sixty-five".