20821928 has 8 divisors (see below), whose sum is σ = 39041130. Its totient is φ = 10410960.

The previous prime is 20821909. The next prime is 20821949. The reversal of 20821928 is 82912802.

It can be written as a sum of positive squares in only one way, i.e., 20593444 + 228484 = 4538^2 + 478^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 20821894 and 20821903.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1301363 + ... + 1301378.

Almost surely, 2^20821928 is an apocalyptic number.

It is an amenable number.

20821928 is a deficient number, since it is larger than the sum of its proper divisors (18219202).

20821928 is a wasteful number, since it uses less digits than its factorization.

20821928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2602747 (or 2602743 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 20821928 is about 4563.1050831643. The cubic root of 20821928 is about 275.1103821341.

The spelling of 20821928 in words is "twenty million, eight hundred twenty-one thousand, nine hundred twenty-eight".