21537728 has 14 divisors (see below), whose sum is σ = 42739056. Its totient is φ = 10768832.

The previous prime is 21537689. The next prime is 21537743. The reversal of 21537728 is 82773512.

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, 168200 + ... + 168327.

Almost surely, 2^21537728 is an apocalyptic number.

It is an amenable number.

21537728 is a deficient number, since it is larger than the sum of its proper divisors (21201328).

21537728 is an equidigital number, since it uses as much as digits as its factorization.

21537728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336539 (or 336529 counting only the distinct ones).

The product of its digits is 23520, while the sum is 35.

The square root of 21537728 is about 4640.8757794192. The cubic root of 21537728 is about 278.2274418404.

The spelling of 21537728 in words is "twenty-one million, five hundred thirty-seven thousand, seven hundred twenty-eight".