21543543 has 32 divisors (see below), whose sum is σ = 37662720. Its totient is φ = 11910240.

The previous prime is 21543527. The next prime is 21543551. The reversal of 21543543 is 34534512.

It is not a de Polignac number, because 21543543 - 2⁴ = 21543527 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543503) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4021 + ... + 7697.

It is an arithmetic number, because the mean of its divisors is an integer number (1176960).

Almost surely, 2^21543543 is an apocalyptic number.

21543543 is a deficient number, since it is larger than the sum of its proper divisors (16119177).

21543543 is a wasteful number, since it uses less digits than its factorization.

21543543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3724 (or 3718 counting only the distinct ones).

The product of its digits is 7200, while the sum is 27.

The square root of 21543543 is about 4641.5022352682. The cubic root of 21543543 is about 278.2524792537.

The spelling of 21543543 in words is "twenty-one million, five hundred forty-three thousand, five hundred forty-three".