20666728 has 8 divisors (see below), whose sum is σ = 38750130. Its totient is φ = 10333360.

The previous prime is 20666689. The next prime is 20666743. The reversal of 20666728 is 82766602.

It can be written as a sum of positive squares in only one way, i.e., 18301284 + 2365444 = 4278^2 + 1538^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×20666728² = 854227292451968, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1291663 + ... + 1291678.

Almost surely, 2^20666728 is an apocalyptic number.

It is an amenable number.

20666728 is a deficient number, since it is larger than the sum of its proper divisors (18083402).

20666728 is a wasteful number, since it uses less digits than its factorization.

20666728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2583347 (or 2583343 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 37.

The square root of 20666728 is about 4546.0673114242. The cubic root of 20666728 is about 274.4251484968.

The spelling of 20666728 in words is "twenty million, six hundred sixty-six thousand, seven hundred twenty-eight".