21030728 has 16 divisors (see below), whose sum is σ = 39565680. Its totient is φ = 10479888.

The previous prime is 21030721. The next prime is 21030767. The reversal of 21030728 is 82703012.

It is not an unprimeable number, because it can be changed into a prime (21030721) 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, 1826 + ... + 6737.

It is an arithmetic number, because the mean of its divisors is an integer number (2472855).

Almost surely, 2^21030728 is an apocalyptic number.

It is an amenable number.

21030728 is a deficient number, since it is larger than the sum of its proper divisors (18534952).

21030728 is a wasteful number, since it uses less digits than its factorization.

21030728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8876 (or 8872 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21030728 is about 4585.9271690684. The cubic root of 21030728 is about 276.0269174896.

The spelling of 21030728 in words is "twenty-one million, thirty thousand, seven hundred twenty-eight".