42021 has 24 divisors (see below), whose sum is σ = 74880. Its totient is φ = 22176.

The previous prime is 42019. The next prime is 42023. The reversal of 42021 is 12024.

42021 is nontrivially palindromic in base 2.

It is an interprime number because it is at equal distance from previous prime (42019) and next prime (42023).

It is not a de Polignac number, because 42021 - 2¹ = 42019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 41994 and 42012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1435 + ... + 1463.

It is an arithmetic number, because the mean of its divisors is an integer number (3120).

2⁴²⁰²¹ is an apocalyptic number.

It is an amenable number.

42021 is a deficient number, since it is larger than the sum of its proper divisors (32859).

42021 is a wasteful number, since it uses less digits than its factorization.

42021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65 (or 62 counting only the distinct ones).

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

The square root of 42021 is about 204.9902436703. The cubic root of 42021 is about 34.7660588613.

Adding to 42021 its reverse (12024), we get a palindrome (54045).

It can be divided in two parts, 420 and 21, that added together give a square (441 = 21²).

The spelling of 42021 in words is "forty-two thousand, twenty-one", and thus it is an iban number.