21069728 has 24 divisors (see below), whose sum is σ = 41648292. Its totient is φ = 10492416.

The previous prime is 21069707. The next prime is 21069733. The reversal of 21069728 is 82796012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 19963024 + 1106704 = 4468^2 + 1052^2 .

It is a zygodrome in base 4.

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, 7676 + ... + 10052.

Almost surely, 2^21069728 is an apocalyptic number.

It is an amenable number.

21069728 is a deficient number, since it is larger than the sum of its proper divisors (20578564).

21069728 is a wasteful number, since it uses less digits than its factorization.

21069728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2664 (or 2656 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21069728 is about 4590.1773386221. The cubic root of 21069728 is about 276.1974362703.

The spelling of 21069728 in words is "twenty-one million, sixty-nine thousand, seven hundred twenty-eight".