261422561 has 4 divisors (see below), whose sum is σ = 261906324. Its totient is φ = 260938800.

The previous prime is 261422521. The next prime is 261422573. The reversal of 261422561 is 165224162.

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 208947025 + 52475536 = 14455^2 + 7244^2 .

It is a cyclic number.

It is not a de Polignac number, because 261422561 - 2²⁶ = 194313697 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (261422521) 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, 241070 + ... + 242151.

It is an arithmetic number, because the mean of its divisors is an integer number (65476581).

Almost surely, 2^261422561 is an apocalyptic number.

It is an amenable number.

261422561 is a deficient number, since it is larger than the sum of its proper divisors (483763).

261422561 is an equidigital number, since it uses as much as digits as its factorization.

261422561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 483762.

The product of its digits is 5760, while the sum is 29.

The square root of 261422561 is about 16168.5670669976. The cubic root of 261422561 is about 639.4123520256.

The spelling of 261422561 in words is "two hundred sixty-one million, four hundred twenty-two thousand, five hundred sixty-one".