21543556 has 12 divisors (see below), whose sum is σ = 39919068. Its totient is φ = 10138112.

The previous prime is 21543551. The next prime is 21543569. The reversal of 21543556 is 65534512.

It can be written as a sum of positive squares in 2 ways, for example, as 13075456 + 8468100 = 3616^2 + 2910^2 .

It is not an unprimeable number, because it can be changed into a prime (21543551) 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, 158341 + ... + 158476.

It is an arithmetic number, because the mean of its divisors is an integer number (3326589).

Almost surely, 2^21543556 is an apocalyptic number.

It is an amenable number.

21543556 is a deficient number, since it is larger than the sum of its proper divisors (18375512).

21543556 is a wasteful number, since it uses less digits than its factorization.

21543556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316838 (or 316836 counting only the distinct ones).

The product of its digits is 18000, while the sum is 31.

The square root of 21543556 is about 4641.5036356767. The cubic root of 21543556 is about 278.2525352222.

The spelling of 21543556 in words is "twenty-one million, five hundred forty-three thousand, five hundred fifty-six".