261660541 has 4 divisors (see below), whose sum is σ = 262655712. Its totient is φ = 260665372.

The previous prime is 261660521. The next prime is 261660551. The reversal of 261660541 is 145066162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 145066162 = 2 ⋅72533081.

It is a cyclic number.

It is not a de Polignac number, because 261660541 - 2¹¹ = 261658493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261660521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 497191 + ... + 497716.

It is an arithmetic number, because the mean of its divisors is an integer number (65663928).

Almost surely, 2^261660541 is an apocalyptic number.

It is an amenable number.

261660541 is a deficient number, since it is larger than the sum of its proper divisors (995171).

261660541 is an equidigital number, since it uses as much as digits as its factorization.

261660541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 995170.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 261660541 is about 16175.9247339990. The cubic root of 261660541 is about 639.6063179433.

The spelling of 261660541 in words is "two hundred sixty-one million, six hundred sixty thousand, five hundred forty-one".