21146728 has 8 divisors (see below), whose sum is σ = 39650130. Its totient is φ = 10573360.

The previous prime is 21146717. The next prime is 21146747. The reversal of 21146728 is 82764112.

It can be written as a sum of positive squares in only one way, i.e., 19554084 + 1592644 = 4422^2 + 1262^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21146728.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1321663 + ... + 1321678.

Almost surely, 2^21146728 is an apocalyptic number.

It is an amenable number.

21146728 is a deficient number, since it is larger than the sum of its proper divisors (18503402).

21146728 is a wasteful number, since it uses less digits than its factorization.

21146728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2643347 (or 2643343 counting only the distinct ones).

The product of its digits is 5376, while the sum is 31.

The square root of 21146728 is about 4598.5571650247. The cubic root of 21146728 is about 276.5334847128.

The spelling of 21146728 in words is "twenty-one million, one hundred forty-six thousand, seven hundred twenty-eight".