4020021 has 12 divisors (see below), whose sum is σ = 5835648. Its totient is φ = 2666664.

The previous prime is 4020017. The next prime is 4020031. The reversal of 4020021 is 1200204.

It is not a de Polignac number, because 4020021 - 2² = 4020017 is a prime.

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

It is a junction number, because it is equal to n+sod(n) for n = 4019985 and 4020012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4020011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1006 + ... + 3008.

It is an arithmetic number, because the mean of its divisors is an integer number (486304).

Almost surely, 2^4020021 is an apocalyptic number.

It is an amenable number.

4020021 is a deficient number, since it is larger than the sum of its proper divisors (1815627).

4020021 is a wasteful number, since it uses less digits than its factorization.

4020021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2232 (or 2229 counting only the distinct ones).

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

The square root of 4020021 is about 2004.9990024935. Note that the first 3 decimals coincide. The cubic root of 4020021 is about 159.0045091874.

Adding to 4020021 its reverse (1200204), we get a palindrome (5220225).

The spelling of 4020021 in words is "four million, twenty thousand, twenty-one".