21006213 has 4 divisors (see below), whose sum is σ = 28008288. Its totient is φ = 14004140.

The previous prime is 21006163. The next prime is 21006217. The reversal of 21006213 is 31260012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21006213 - 2⁹ = 21005701 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21006192 and 21006201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006217) 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, 3501033 + ... + 3501038.

It is an arithmetic number, because the mean of its divisors is an integer number (7002072).

Almost surely, 2^21006213 is an apocalyptic number.

It is an amenable number.

21006213 is a deficient number, since it is larger than the sum of its proper divisors (7002075).

21006213 is an equidigital number, since it uses as much as digits as its factorization.

21006213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7002074.

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21006213 is about 4583.2535386993. The cubic root of 21006213 is about 275.9196232028.

Adding to 21006213 its reverse (31260012), we get a palindrome (52266225).

The spelling of 21006213 in words is "twenty-one million, six thousand, two hundred thirteen".