261997 has 8 divisors (see below), whose sum is σ = 275576. Its totient is φ = 248832.

The previous prime is 261983. The next prime is 262007. The reversal of 261997 is 799162.

It can be written as a sum of positive squares in 4 ways, for example, as 90601 + 171396 = 301^2 + 414^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 5-Lehmer number, since φ(261997) divides (261997-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 261997 - 2¹¹ = 259949 is a prime.

261997 is a lucky number.

It is a nialpdrome in base 8.

It is a zygodrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261917) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2653 + ... + 2749.

It is an arithmetic number, because the mean of its divisors is an integer number (34447).

2²⁶¹⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

261997 is a deficient number, since it is larger than the sum of its proper divisors (13579).

261997 is an equidigital number, since it uses as much as digits as its factorization.

261997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207.

The product of its digits is 6804, while the sum is 34.

The square root of 261997 is about 511.8564251819. The cubic root of 261997 is about 63.9880348726.

The spelling of 261997 in words is "two hundred sixty-one thousand, nine hundred ninety-seven".