21305143 has 4 divisors (see below), whose sum is σ = 21316680. Its totient is φ = 21293608.

The previous prime is 21305113. The next prime is 21305149. The reversal of 21305143 is 34150312.

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-21305143 is a prime.

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 21305143.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305149) 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, 2305 + ... + 6922.

It is an arithmetic number, because the mean of its divisors is an integer number (5329170).

Almost surely, 2^21305143 is an apocalyptic number.

21305143 is a deficient number, since it is larger than the sum of its proper divisors (11537).

21305143 is an equidigital number, since it uses as much as digits as its factorization.

21305143 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11536.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21305143 is about 4615.7494516059. The cubic root of 21305143 is about 277.2222928571. Note that the first 4 decimals are identical.

Adding to 21305143 its reverse (34150312), we get a palindrome (55455455).

The spelling of 21305143 in words is "twenty-one million, three hundred five thousand, one hundred forty-three".