261308657 has 4 divisors (see below), whose sum is σ = 261705840. Its totient is φ = 260911476.

The previous prime is 261308639. The next prime is 261308687. The reversal of 261308657 is 756803162.

261308657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is a cyclic number.

It is not a de Polignac number, because 261308657 - 2¹⁰ = 261307633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261308657.

It is not an unprimeable number, because it can be changed into a prime (261308687) 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, 197603 + ... + 198920.

It is an arithmetic number, because the mean of its divisors is an integer number (65426460).

Almost surely, 2^261308657 is an apocalyptic number.

It is an amenable number.

261308657 is a deficient number, since it is larger than the sum of its proper divisors (397183).

261308657 is an equidigital number, since it uses as much as digits as its factorization.

261308657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 397182.

The product of its (nonzero) digits is 60480, while the sum is 38.

The square root of 261308657 is about 16165.0442931654. The cubic root of 261308657 is about 639.3194727620.

The spelling of 261308657 in words is "two hundred sixty-one million, three hundred eight thousand, six hundred fifty-seven".