21312213 has 8 divisors (see below), whose sum is σ = 30602208. Its totient is φ = 13115184.

The previous prime is 21312173. The next prime is 21312223. The reversal of 21312213 is 31221312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21312213 - 2⁶ = 21312149 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21312192 and 21312201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 273195 + ... + 273272.

It is an arithmetic number, because the mean of its divisors is an integer number (3825276).

Almost surely, 2^21312213 is an apocalyptic number.

It is an amenable number.

21312213 is a deficient number, since it is larger than the sum of its proper divisors (9289995).

21312213 is a wasteful number, since it uses less digits than its factorization.

21312213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546483.

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

The square root of 21312213 is about 4616.5152442075. The cubic root of 21312213 is about 277.2529543871.

Adding to 21312213 its reverse (31221312), we get a palindrome (52533525).

Subtracting 21312213 from its reverse (31221312), we obtain a palindrome (9909099).

The spelling of 21312213 in words is "twenty-one million, three hundred twelve thousand, two hundred thirteen".