21028816 has 10 divisors (see below), whose sum is σ = 40743362. Its totient is φ = 10514400.

The previous prime is 21028771. The next prime is 21028823. The reversal of 21028816 is 61882012.

It can be written as a sum of positive squares in only one way, i.e., 10916416 + 10112400 = 3304^2 + 3180^2 .

It is a super-2 number, since 2×21028816² = 884422204723712, which contains 22 as substring.

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, 657135 + ... + 657166.

Almost surely, 2^21028816 is an apocalyptic number.

It is an amenable number.

21028816 is a deficient number, since it is larger than the sum of its proper divisors (19714546).

21028816 is a wasteful number, since it uses less digits than its factorization.

21028816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1314309 (or 1314303 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21028816 is about 4585.7187004874. The cubic root of 21028816 is about 276.0185522781.

The spelling of 21028816 in words is "twenty-one million, twenty-eight thousand, eight hundred sixteen".