21280543 has 4 divisors (see below), whose sum is σ = 22205808. Its totient is φ = 20355280.

The previous prime is 21280529. The next prime is 21280547. The reversal of 21280543 is 34508212.

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 21280543 - 2¹³ = 21272351 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 (21280547) 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, 462598 + ... + 462643.

It is an arithmetic number, because the mean of its divisors is an integer number (5551452).

Almost surely, 2^21280543 is an apocalyptic number.

21280543 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21280543 is a deficient number, since it is larger than the sum of its proper divisors (925265).

21280543 is an equidigital number, since it uses as much as digits as its factorization.

21280543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 925264.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 21280543 is about 4613.0838925821. The cubic root of 21280543 is about 277.1155534520.

Adding to 21280543 its reverse (34508212), we get a palindrome (55788755).

The spelling of 21280543 in words is "twenty-one million, two hundred eighty thousand, five hundred forty-three".