261951 has 4 divisors (see below), whose sum is σ = 349272. Its totient is φ = 174632.

The previous prime is 261917. The next prime is 261959. The reversal of 261951 is 159162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261951 - 2⁶ = 261887 is a prime.

It is a D-number.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261959) 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, 43656 + ... + 43661.

It is an arithmetic number, because the mean of its divisors is an integer number (87318).

2²⁶¹⁹⁵¹ is an apocalyptic number.

261951 is a deficient number, since it is larger than the sum of its proper divisors (87321).

261951 is an equidigital number, since it uses as much as digits as its factorization.

261951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87320.

The product of its digits is 540, while the sum is 24.

The square root of 261951 is about 511.8114887339. The cubic root of 261951 is about 63.9842897637.

The spelling of 261951 in words is "two hundred sixty-one thousand, nine hundred fifty-one".