21252813 has 4 divisors (see below), whose sum is σ = 28337088. Its totient is φ = 14168540.

The previous prime is 21252809. The next prime is 21252821. The reversal of 21252813 is 31825212.

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 21252813 - 2² = 21252809 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252893) 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 3 ways as a sum of consecutive naturals, for example, 3542133 + ... + 3542138.

It is an arithmetic number, because the mean of its divisors is an integer number (7084272).

Almost surely, 2^21252813 is an apocalyptic number.

It is an amenable number.

21252813 is a deficient number, since it is larger than the sum of its proper divisors (7084275).

21252813 is an equidigital number, since it uses as much as digits as its factorization.

21252813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7084274.

The product of its digits is 960, while the sum is 24.

The square root of 21252813 is about 4610.0773312386. The cubic root of 21252813 is about 276.9951343053.

The spelling of 21252813 in words is "twenty-one million, two hundred fifty-two thousand, eight hundred thirteen".