21310728 has 16 divisors (see below), whose sum is σ = 53276880. Its totient is φ = 7103568.

The previous prime is 21310669. The next prime is 21310739. The reversal of 21310728 is 82701312.

It is a super-3 number, since 3×21310728³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 887947 = 21310728 / (2 + 1 + 3 + 1 + 0 + 7 + 2 + 8).

It is a junction number, because it is equal to n+sod(n) for n = 21310698 and 21310707.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 443950 + ... + 443997.

It is an arithmetic number, because the mean of its divisors is an integer number (3329805).

Almost surely, 2^21310728 is an apocalyptic number.

It is an amenable number.

21310728 is an abundant number, since it is smaller than the sum of its proper divisors (31966152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21310728 is a wasteful number, since it uses less digits than its factorization.

21310728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 887956 (or 887952 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21310728 is about 4616.3544058055. The cubic root of 21310728 is about 277.2465147274.

It can be divided in two parts, 2131072 and 8, that added together give a triangular number (2131080 = T₂₀₆₄).

The spelling of 21310728 in words is "twenty-one million, three hundred ten thousand, seven hundred twenty-eight".