21420211 has 4 divisors (see below), whose sum is σ = 21771424. Its totient is φ = 21069000.

The previous prime is 21420209. The next prime is 21420227. The reversal of 21420211 is 11202412.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21420211 - 2¹ = 21420209 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420191 and 21420200.

It is not an unprimeable number, because it can be changed into a prime (21420251) 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, 175515 + ... + 175636.

It is an arithmetic number, because the mean of its divisors is an integer number (5442856).

Almost surely, 2^21420211 is an apocalyptic number.

21420211 is a deficient number, since it is larger than the sum of its proper divisors (351213).

21420211 is an equidigital number, since it uses as much as digits as its factorization.

21420211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351212.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21420211 is about 4628.1973812706. The cubic root of 21420211 is about 277.7204848891.

Adding to 21420211 its reverse (11202412), we get a palindrome (32622623).

The spelling of 21420211 in words is "twenty-one million, four hundred twenty thousand, two hundred eleven".