210920021 has 4 divisors (see below), whose sum is σ = 227144652. Its totient is φ = 194695392.

The previous prime is 210920011. The next prime is 210920023. The reversal of 210920021 is 120029012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 137217796 + 73702225 = 11714^2 + 8585^2 .

It is a cyclic number.

It is not a de Polignac number, because 210920021 - 2¹⁰ = 210918997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210920023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8112296 + ... + 8112321.

It is an arithmetic number, because the mean of its divisors is an integer number (56786163).

Almost surely, 2^210920021 is an apocalyptic number.

It is an amenable number.

210920021 is a deficient number, since it is larger than the sum of its proper divisors (16224631).

210920021 is a wasteful number, since it uses less digits than its factorization.

210920021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16224630.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 210920021 is about 14523.0857946925. The cubic root of 210920021 is about 595.2589518514.

Adding to 210920021 its reverse (120029012), we get a palindrome (330949033).

The spelling of 210920021 in words is "two hundred ten million, nine hundred twenty thousand, twenty-one".