21543664 has 10 divisors (see below), whose sum is σ = 41740880. Its totient is φ = 10771824.

The previous prime is 21543659. The next prime is 21543677. The reversal of 21543664 is 46634512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 673224 + ... + 673255.

It is an arithmetic number, because the mean of its divisors is an integer number (4174088).

Almost surely, 2^21543664 is an apocalyptic number.

It is an amenable number.

21543664 is a deficient number, since it is larger than the sum of its proper divisors (20197216).

21543664 is a wasteful number, since it uses less digits than its factorization.

21543664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1346487 (or 1346481 counting only the distinct ones).

The product of its digits is 17280, while the sum is 31.

The square root of 21543664 is about 4641.5152698230. The cubic root of 21543664 is about 278.2530001907.

The spelling of 21543664 in words is "twenty-one million, five hundred forty-three thousand, six hundred sixty-four".