40021 has 4 divisors (see below), whose sum is σ = 41344.
Its totient is φ = 38700.
The previous prime is 40013. The next prime is 40031. The reversal of 40021 is 12004.
Adding to 40021 its reverse (12004), we get a palindrome (52025).
40021 is nontrivially palindromic in base 12.
40021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.
It is a cyclic number.
It is not a de Polignac number, because 40021 - 23 = 40013 is a prime.
It is a Duffinian number.
40021 is an undulating number in base 12.
It is a junction number, because it is equal to n+sod(n) for n = 39986 and 40013.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (40031) 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, 615 + ... + 676.
It is an arithmetic number, because the mean of its divisors is an integer number (10336).
240021 is an apocalyptic number.
40021 is the 116-th hex number.
It is an amenable number.
40021 is a deficient number, since it is larger than the sum of its proper divisors (1323).
40021 is a wasteful number, since it uses less digits than its factorization.
40021 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 1322.
The product of its (nonzero) digits is 8, while the sum is 7.
The square root of 40021 is about 200.0524931112.
The cubic root of 40021 is about 34.2055028023.
The spelling of 40021 in words is "forty thousand, twenty-one", and thus it is an iban number.