210320021 has 4 divisors (see below), whose sum is σ = 210470700. Its totient is φ = 210169344.

The previous prime is 210319979. The next prime is 210320023. The reversal of 210320021 is 120023012.

It is a happy number.

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 45711121 + 164608900 = 6761^2 + 12830^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-210320021 is a prime.

It is a super-2 number, since 2×210320021² = 88469022466880882, which contains 22 as substring.

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 = 210319984 and 210320011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210320023) 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, 73226 + ... + 76043.

It is an arithmetic number, because the mean of its divisors is an integer number (52617675).

Almost surely, 2^210320021 is an apocalyptic number.

It is an amenable number.

210320021 is a deficient number, since it is larger than the sum of its proper divisors (150679).

210320021 is a wasteful number, since it uses less digits than its factorization.

210320021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150678.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 210320021 is about 14502.4143162440. The cubic root of 210320021 is about 594.6939753421.

Adding to 210320021 its reverse (120023012), we get a palindrome (330343033).

The spelling of 210320021 in words is "two hundred ten million, three hundred twenty thousand, twenty-one".