21371543 has 4 divisors (see below), whose sum is σ = 21416640. Its totient is φ = 21326448.

The previous prime is 21371509. The next prime is 21371551. The reversal of 21371543 is 34517312.

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 21371543 - 2⁶ = 21371479 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 (21371843) 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, 21830 + ... + 22787.

It is an arithmetic number, because the mean of its divisors is an integer number (5354160).

Almost surely, 2^21371543 is an apocalyptic number.

21371543 is a deficient number, since it is larger than the sum of its proper divisors (45097).

21371543 is an equidigital number, since it uses as much as digits as its factorization.

21371543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45096.

The product of its digits is 2520, while the sum is 26.

The square root of 21371543 is about 4622.9366208072. The cubic root of 21371543 is about 277.5099928766.

Adding to 21371543 its reverse (34517312), we get a palindrome (55888855).

The spelling of 21371543 in words is "twenty-one million, three hundred seventy-one thousand, five hundred forty-three".