261397 has 4 divisors (see below), whose sum is σ = 267520. Its totient is φ = 255276.

The previous prime is 261389. The next prime is 261407. The reversal of 261397 is 793162.

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: 793162 = 2 ⋅396581.

It is a cyclic number.

It is not a de Polignac number, because 261397 - 2³ = 261389 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 (261337) 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, 2997 + ... + 3082.

It is an arithmetic number, because the mean of its divisors is an integer number (66880).

2²⁶¹³⁹⁷ is an apocalyptic number.

It is an amenable number.

261397 is a deficient number, since it is larger than the sum of its proper divisors (6123).

261397 is an equidigital number, since it uses as much as digits as its factorization.

261397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6122.

The product of its digits is 2268, while the sum is 28.

The square root of 261397 is about 511.2699873844. The cubic root of 261397 is about 63.9391511499.

The spelling of 261397 in words is "two hundred sixty-one thousand, three hundred ninety-seven".