20021001 has 64 divisors (see below), whose sum is σ = 36771840. Its totient is φ = 9354240.

The previous prime is 20020943. The next prime is 20021021. The reversal of 20021001 is 10012002.

It is a happy number.

It is not a de Polignac number, because 20021001 - 2⁶ = 20020937 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20021021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 177121 + ... + 177233.

It is an arithmetic number, because the mean of its divisors is an integer number (574560).

Almost surely, 2^20021001 is an apocalyptic number.

20021001 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20021001 is a deficient number, since it is larger than the sum of its proper divisors (16750839).

20021001 is a wasteful number, since it uses less digits than its factorization.

20021001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206.

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 20021001 is about 4474.4833221278. The cubic root of 20021001 is about 271.5367375647.

Adding to 20021001 its reverse (10012002), we get a palindrome (30033003).

It can be divided in two parts, 2002 and 1001, that multiplied together give a palindrome (2004002).

The spelling of 20021001 in words is "twenty million, twenty-one thousand, one".