20040021 has 32 divisors (see below), whose sum is σ = 31194240. Its totient is φ = 12700800.

The previous prime is 20039993. The next prime is 20040049. The reversal of 20040021 is 12004002.

It is an interprime number because it is at equal distance from previous prime (20039993) and next prime (20040049).

It is not a de Polignac number, because 20040021 - 2⁷ = 20039893 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 = 20039985 and 20040012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20040071) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 47391 + ... + 47811.

It is an arithmetic number, because the mean of its divisors is an integer number (974820).

Almost surely, 2^20040021 is an apocalyptic number.

It is an amenable number.

20040021 is a deficient number, since it is larger than the sum of its proper divisors (11154219).

20040021 is a wasteful number, since it uses less digits than its factorization.

20040021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 514 (or 508 counting only the distinct ones).

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

The square root of 20040021 is about 4476.6082026463. The cubic root of 20040021 is about 271.6226972051.

Adding to 20040021 its reverse (12004002), we get a palindrome (32044023).

The spelling of 20040021 in words is "twenty million, forty thousand, twenty-one".