21213203 has 4 divisors (see below), whose sum is σ = 23141688. Its totient is φ = 19284720.

The previous prime is 21213193. The next prime is 21213251. The reversal of 21213203 is 30231212.

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 21213203 - 2⁴ = 21213187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213293) 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, 964226 + ... + 964247.

It is an arithmetic number, because the mean of its divisors is an integer number (5785422).

Almost surely, 2^21213203 is an apocalyptic number.

21213203 is a deficient number, since it is larger than the sum of its proper divisors (1928485).

21213203 is a wasteful number, since it uses less digits than its factorization.

21213203 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1928484.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21213203 is about 4605.7793043089. The cubic root of 21213203 is about 276.8229437570.

Adding to 21213203 its reverse (30231212), we get a palindrome (51444415).

Subtracting 21213203 from its reverse (30231212), we obtain a square (9018009 = 3003²).

The spelling of 21213203 in words is "twenty-one million, two hundred thirteen thousand, two hundred three".