261621361 has 4 divisors (see below), whose sum is σ = 262362852. Its totient is φ = 260879872.

The previous prime is 261621341. The next prime is 261621401. The reversal of 261621361 is 163126162.

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 164480625 + 97140736 = 12825^2 + 9856^2 .

It is a cyclic number.

It is not a de Polignac number, because 261621361 - 2⁷ = 261621233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261621341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 370216 + ... + 370921.

It is an arithmetic number, because the mean of its divisors is an integer number (65590713).

Almost surely, 2^261621361 is an apocalyptic number.

It is an amenable number.

261621361 is a deficient number, since it is larger than the sum of its proper divisors (741491).

261621361 is an equidigital number, since it uses as much as digits as its factorization.

261621361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 741490.

The product of its digits is 2592, while the sum is 28.

The square root of 261621361 is about 16174.7136296134. The cubic root of 261621361 is about 639.5743923215.

The spelling of 261621361 in words is "two hundred sixty-one million, six hundred twenty-one thousand, three hundred sixty-one".