210020021 has 4 divisors (see below), whose sum is σ = 210200544. Its totient is φ = 209839500.

The previous prime is 210020003. The next prime is 210020039. The reversal of 210020021 is 120020012.

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 an interprime number because it is at equal distance from previous prime (210020003) and next prime (210020039).

It is a cyclic number.

It is not a de Polignac number, because 210020021 - 2¹⁰ = 210018997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 210019990 and 210020008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210020221) 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 3 ways as a sum of consecutive naturals, for example, 88505 + ... + 90846.

It is an arithmetic number, because the mean of its divisors is an integer number (52550136).

Almost surely, 2^210020021 is an apocalyptic number.

It is an amenable number.

210020021 is a deficient number, since it is larger than the sum of its proper divisors (180523).

210020021 is a wasteful number, since it uses less digits than its factorization.

210020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180522.

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 210020021 is about 14492.0675198537. The cubic root of 210020021 is about 594.4110840826.

Adding to 210020021 its reverse (120020012), we get a palindrome (330040033).

Subtracting from 210020021 its reverse (120020012), we obtain a palindrome (90000009).

The spelling of 210020021 in words is "two hundred ten million, twenty thousand, twenty-one".