21305299 has 4 divisors (see below), whose sum is σ = 21317320. Its totient is φ = 21293280.

The previous prime is 21305293. The next prime is 21305309. The reversal of 21305299 is 99250312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21305299 is a prime.

It is a super-3 number, since 3×21305299³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21305299.

It is not an unprimeable number, because it can be changed into a prime (21305293) 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 3 ways as a sum of consecutive naturals, for example, 2769 + ... + 7090.

It is an arithmetic number, because the mean of its divisors is an integer number (5329330).

Almost surely, 2^21305299 is an apocalyptic number.

21305299 is a deficient number, since it is larger than the sum of its proper divisors (12021).

21305299 is an equidigital number, since it uses as much as digits as its factorization.

21305299 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12020.

The product of its (nonzero) digits is 4860, while the sum is 31.

The square root of 21305299 is about 4615.7663502391. The cubic root of 21305299 is about 277.2229694788. Note that the first 3 decimals are identical.

The spelling of 21305299 in words is "twenty-one million, three hundred five thousand, two hundred ninety-nine".