21213543 has 32 divisors (see below), whose sum is σ = 31928512. Its totient is φ = 12441600.

The previous prime is 21213487. The next prime is 21213553. The reversal of 21213543 is 34531212.

It is not a de Polignac number, because 21213543 - 2⁸ = 21213287 is a prime.

It is a super-2 number, since 2×21213543² = 900028813225698, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213553) 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 31 ways as a sum of consecutive naturals, for example, 87903 + ... + 88143.

It is an arithmetic number, because the mean of its divisors is an integer number (997766).

Almost surely, 2^21213543 is an apocalyptic number.

21213543 is a deficient number, since it is larger than the sum of its proper divisors (10714969).

21213543 is a wasteful number, since it uses less digits than its factorization.

21213543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 355.

The product of its digits is 720, while the sum is 21.

The square root of 21213543 is about 4605.8162143099. The cubic root of 21213543 is about 276.8244226992.

Adding to 21213543 its reverse (34531212), we get a palindrome (55744755).

The spelling of 21213543 in words is "twenty-one million, two hundred thirteen thousand, five hundred forty-three".