21798213 has 4 divisors (see below), whose sum is σ = 29064288. Its totient is φ = 14532140.

The previous prime is 21798197. The next prime is 21798221. The reversal of 21798213 is 31289712.

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 21798213 - 2⁴ = 21798197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21798113) 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, 3633033 + ... + 3633038.

It is an arithmetic number, because the mean of its divisors is an integer number (7266072).

Almost surely, 2^21798213 is an apocalyptic number.

It is an amenable number.

21798213 is a deficient number, since it is larger than the sum of its proper divisors (7266075).

21798213 is an equidigital number, since it uses as much as digits as its factorization.

21798213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7266074.

The product of its digits is 6048, while the sum is 33.

The square root of 21798213 is about 4668.8556413751. The cubic root of 21798213 is about 279.3446108510.

The spelling of 21798213 in words is "twenty-one million, seven hundred ninety-eight thousand, two hundred thirteen".