259821 has 8 divisors (see below), whose sum is σ = 384960. Its totient is φ = 173196.

The previous prime is 259813. The next prime is 259823. The reversal of 259821 is 128952.

It is not a de Polignac number, because 259821 - 2³ = 259813 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 9623 = 259821 / (2 + 5 + 9 + 8 + 2 + 1).

It is a Curzon number.

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 (259823) 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, 4785 + ... + 4838.

It is an arithmetic number, because the mean of its divisors is an integer number (48120).

2²⁵⁹⁸²¹ is an apocalyptic number.

It is an amenable number.

259821 is a deficient number, since it is larger than the sum of its proper divisors (125139).

259821 is an equidigital number, since it uses as much as digits as its factorization.

259821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9632 (or 9626 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 259821 is about 509.7263971976. The cubic root of 259821 is about 63.8103925969.

The spelling of 259821 in words is "two hundred fifty-nine thousand, eight hundred twenty-one".