21013211 has 4 divisors (see below), whose sum is σ = 21026952. Its totient is φ = 20999472.

The previous prime is 21013189. The next prime is 21013217. The reversal of 21013211 is 11231012.

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-21013211 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013192 and 21013201.

It is not an unprimeable number, because it can be changed into a prime (21013217) 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 3 ways as a sum of consecutive naturals, for example, 4241 + ... + 7746.

It is an arithmetic number, because the mean of its divisors is an integer number (5256738).

Almost surely, 2^21013211 is an apocalyptic number.

21013211 is a deficient number, since it is larger than the sum of its proper divisors (13741).

21013211 is a wasteful number, since it uses less digits than its factorization.

21013211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13740.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21013211 is about 4584.0169066006. The cubic root of 21013211 is about 275.9502597125.

Adding to 21013211 its reverse (11231012), we get a palindrome (32244223).

The spelling of 21013211 in words is "twenty-one million, thirteen thousand, two hundred eleven".