21210331 has 4 divisors (see below), whose sum is σ = 21262600. Its totient is φ = 21158064.

The previous prime is 21210317. The next prime is 21210337. The reversal of 21210331 is 13301212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21210331 is a prime.

It is a super-2 number, since 2×21210331² = 899756282259122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210337) 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, 25521 + ... + 26338.

It is an arithmetic number, because the mean of its divisors is an integer number (5315650).

Almost surely, 2^21210331 is an apocalyptic number.

21210331 is a deficient number, since it is larger than the sum of its proper divisors (52269).

21210331 is an equidigital number, since it uses as much as digits as its factorization.

21210331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52268.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21210331 is about 4605.4675115562. The cubic root of 21210331 is about 276.8104504154.

Adding to 21210331 its reverse (13301212), we get a palindrome (34511543).

The spelling of 21210331 in words is "twenty-one million, two hundred ten thousand, three hundred thirty-one".