21358813 has 4 divisors (see below), whose sum is σ = 24410080. Its totient is φ = 18307548.

The previous prime is 21358811. The next prime is 21358837. The reversal of 21358813 is 31885312.

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 not a de Polignac number, because 21358813 - 2¹ = 21358811 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 (21358811) 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, 1525623 + ... + 1525636.

It is an arithmetic number, because the mean of its divisors is an integer number (6102520).

Almost surely, 2^21358813 is an apocalyptic number.

It is an amenable number.

21358813 is a deficient number, since it is larger than the sum of its proper divisors (3051267).

21358813 is an equidigital number, since it uses as much as digits as its factorization.

21358813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3051266.

The product of its digits is 5760, while the sum is 31.

The square root of 21358813 is about 4621.5595852483. The cubic root of 21358813 is about 277.4548821489.

The spelling of 21358813 in words is "twenty-one million, three hundred fifty-eight thousand, eight hundred thirteen".