21212513 has 4 divisors (see below), whose sum is σ = 24242880. Its totient is φ = 18182148.

The previous prime is 21212501. The next prime is 21212519. The reversal of 21212513 is 31521212.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21212513 - 2⁴ = 21212497 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21212491 and 21212500.

It is not an unprimeable number, because it can be changed into a prime (21212519) 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, 1515173 + ... + 1515186.

It is an arithmetic number, because the mean of its divisors is an integer number (6060720).

Almost surely, 2^21212513 is an apocalyptic number.

It is an amenable number.

21212513 is a deficient number, since it is larger than the sum of its proper divisors (3030367).

21212513 is an equidigital number, since it uses as much as digits as its factorization.

21212513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3030366.

The product of its digits is 120, while the sum is 17.

The square root of 21212513 is about 4605.7043978093. The cubic root of 21212513 is about 276.8199423259.

Adding to 21212513 its reverse (31521212), we get a palindrome (52733725).

The spelling of 21212513 in words is "twenty-one million, two hundred twelve thousand, five hundred thirteen".