21812813 has 8 divisors (see below), whose sum is σ = 23898240. Its totient is φ = 19744480.

The previous prime is 21812789. The next prime is 21812821. The reversal of 21812813 is 31821812.

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

It is a cyclic number.

It is not a de Polignac number, because 21812813 - 2¹⁶ = 21747277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21812863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1520 + ... + 6777.

It is an arithmetic number, because the mean of its divisors is an integer number (2987280).

Almost surely, 2^21812813 is an apocalyptic number.

It is an amenable number.

21812813 is a deficient number, since it is larger than the sum of its proper divisors (2085427).

21812813 is a wasteful number, since it uses less digits than its factorization.

21812813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8547.

The product of its digits is 768, while the sum is 26.

The square root of 21812813 is about 4670.4189319589. The cubic root of 21812813 is about 279.4069633798.

It can be divided in two parts, 2181 and 2813, that added together give a palindrome (4994).

The spelling of 21812813 in words is "twenty-one million, eight hundred twelve thousand, eight hundred thirteen".