240021 has 6 divisors (see below), whose sum is σ = 346710. Its totient is φ = 160008.

The previous prime is 240017. The next prime is 240041. The reversal of 240021 is 120042.

It can be written as a sum of positive squares in only one way, i.e., 239121 + 900 = 489^2 + 30^2 .

It is not a de Polignac number, because 240021 - 2² = 240017 is a prime.

It is a super-2 number, since 2×240021² = 115220160882, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 26669 = 240021 / (2 + 4 + 0 + 0 + 2 + 1).

It is a Curzon number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 239985 and 240012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (240011) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13326 + ... + 13343.

It is an arithmetic number, because the mean of its divisors is an integer number (57785).

2²⁴⁰⁰²¹ is an apocalyptic number.

It is an amenable number.

240021 is a deficient number, since it is larger than the sum of its proper divisors (106689).

240021 is a wasteful number, since it uses less digits than its factorization.

240021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26675 (or 26672 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 240021 is about 489.9193811231. The cubic root of 240021 is about 62.1464626185.

Adding to 240021 its reverse (120042), we get a palindrome (360063).

The spelling of 240021 in words is "two hundred forty thousand, twenty-one", and thus it is an iban number.