21213207 has 24 divisors (see below), whose sum is σ = 31915520. Its totient is φ = 13562640.

The previous prime is 21213193. The next prime is 21213251. The reversal of 21213207 is 70231212.

It is not a de Polignac number, because 21213207 - 2¹⁰ = 21212183 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21213207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213287) 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 23 ways as a sum of consecutive naturals, for example, 38508 + ... + 39054.

Almost surely, 2^21213207 is an apocalyptic number.

21213207 is a deficient number, since it is larger than the sum of its proper divisors (10702313).

21213207 is a wasteful number, since it uses less digits than its factorization.

21213207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 723 (or 720 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21213207 is about 4605.7797385459. The cubic root of 21213207 is about 276.8229611565.

Adding to 21213207 its reverse (70231212), we get a palindrome (91444419).

The spelling of 21213207 in words is "twenty-one million, two hundred thirteen thousand, two hundred seven".