21821299 has 4 divisors (see below), whose sum is σ = 21955336. Its totient is φ = 21687264.

The previous prime is 21821263. The next prime is 21821309. The reversal of 21821299 is 99212812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21821299 - 2⁷ = 21821171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21821249) 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, 66774 + ... + 67099.

It is an arithmetic number, because the mean of its divisors is an integer number (5488834).

Almost surely, 2^21821299 is an apocalyptic number.

21821299 is a deficient number, since it is larger than the sum of its proper divisors (134037).

21821299 is a wasteful number, since it uses less digits than its factorization.

21821299 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134036.

The product of its digits is 5184, while the sum is 34.

The square root of 21821299 is about 4671.3273274306. The cubic root of 21821299 is about 279.4431919347.

It can be divided in two parts, 2182 and 1299, that added together give a square (3481 = 59²).

The spelling of 21821299 in words is "twenty-one million, eight hundred twenty-one thousand, two hundred ninety-nine".