210210021 has 24 divisors (see below), whose sum is σ = 352199744. Its totient is φ = 118324800.

The previous prime is 210210017. The next prime is 210210047. The reversal of 210210021 is 120012012.

210210021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 210210021 - 2² = 210210017 is a prime.

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

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 = 210209985 and 210210012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210210001) 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, 20680 + ... + 29121.

Almost surely, 2^210210021 is an apocalyptic number.

210210021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

210210021 is a deficient number, since it is larger than the sum of its proper divisors (141989723).

210210021 is a wasteful number, since it uses less digits than its factorization.

210210021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49881 (or 49878 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 210210021 is about 14498.6213482524. The cubic root of 210210021 is about 594.5902798010.

Adding to 210210021 its reverse (120012012), we get a palindrome (330222033).

The spelling of 210210021 in words is "two hundred ten million, two hundred ten thousand, twenty-one".