205761 has 8 divisors (see below), whose sum is σ = 277344. Its totient is φ = 135680.

The previous prime is 205759. The next prime is 205763. The reversal of 205761 is 167502.

205761 is a nontrivial binomial coefficient, being equal to C(642, 2).

It is an interprime number because it is at equal distance from previous prime (205759) and next prime (205763).

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

It is a cyclic number.

It is not a de Polignac number, because 205761 - 2¹ = 205759 is a prime.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (205763) 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, 1 + ... + 641.

It is an arithmetic number, because the mean of its divisors is an integer number (34668).

2²⁰⁵⁷⁶¹ is an apocalyptic number.

205761 is the 641-st triangular number and also the 321-st hexagonal number.

It is an amenable number.

205761 is a deficient number, since it is larger than the sum of its proper divisors (71583).

205761 is a wasteful number, since it uses less digits than its factorization.

205761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 751.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 205761 is about 453.6088623473. The cubic root of 205761 is about 59.0365568713.

The spelling of 205761 in words is "two hundred five thousand, seven hundred sixty-one".