21031213 has 8 divisors (see below), whose sum is σ = 24071040. Its totient is φ = 18000240.

The previous prime is 21031187. The next prime is 21031217. The reversal of 21031213 is 31213012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21031213 - 2⁵ = 21031181 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21031193 and 21031202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4083 + ... + 7663.

It is an arithmetic number, because the mean of its divisors is an integer number (3008880).

Almost surely, 2^21031213 is an apocalyptic number.

It is an amenable number.

21031213 is a deficient number, since it is larger than the sum of its proper divisors (3039827).

21031213 is an equidigital number, since it uses as much as digits as its factorization.

21031213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4427.

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

The square root of 21031213 is about 4585.9800479287. The cubic root of 21031213 is about 276.0290393376.

Adding to 21031213 its reverse (31213012), we get a palindrome (52244225).

The spelling of 21031213 in words is "twenty-one million, thirty-one thousand, two hundred thirteen".