253821 has 16 divisors (see below), whose sum is σ = 367040. Its totient is φ = 155520.

The previous prime is 253819. The next prime is 253823. The reversal of 253821 is 128352.

It is an interprime number because it is at equal distance from previous prime (253819) and next prime (253823).

It is not a de Polignac number, because 253821 - 2¹ = 253819 is a prime.

It is an Ulam number.

It is a Duffinian number.

253821 is an undulating number in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (253823) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3441 + ... + 3513.

It is an arithmetic number, because the mean of its divisors is an integer number (22940).

2²⁵³⁸²¹ is an apocalyptic number.

It is an amenable number.

253821 is a deficient number, since it is larger than the sum of its proper divisors (113219).

253821 is a wasteful number, since it uses less digits than its factorization.

253821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156.

The product of its digits is 480, while the sum is 21.

The square root of 253821 is about 503.8065104780. The cubic root of 253821 is about 63.3153750253.

The spelling of 253821 in words is "two hundred fifty-three thousand, eight hundred twenty-one".