21293728 has 12 divisors (see below), whose sum is σ = 41922090. Its totient is φ = 10646848.

The previous prime is 21293717. The next prime is 21293747. The reversal of 21293728 is 82739212.

It can be written as a sum of positive squares in only one way, i.e., 19254544 + 2039184 = 4388^2 + 1428^2 .

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21293693 and 21293702.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332683 + ... + 332746.

Almost surely, 2^21293728 is an apocalyptic number.

It is an amenable number.

21293728 is a deficient number, since it is larger than the sum of its proper divisors (20628362).

21293728 is an equidigital number, since it uses as much as digits as its factorization.

21293728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665439 (or 665431 counting only the distinct ones).

The product of its digits is 12096, while the sum is 34.

The square root of 21293728 is about 4614.5127586778. The cubic root of 21293728 is about 277.1727733927.

The spelling of 21293728 in words is "twenty-one million, two hundred ninety-three thousand, seven hundred twenty-eight".