21005968 has 10 divisors (see below), whose sum is σ = 40699094. Its totient is φ = 10502976.

The previous prime is 21005953. The next prime is 21005977. The reversal of 21005968 is 86950012.

It can be written as a sum of positive squares in only one way, i.e., 19079424 + 1926544 = 4368^2 + 1388^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 656421 + ... + 656452.

Almost surely, 2^21005968 is an apocalyptic number.

It is an amenable number.

21005968 is a deficient number, since it is larger than the sum of its proper divisors (19693126).

21005968 is a wasteful number, since it uses less digits than its factorization.

21005968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1312881 (or 1312875 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 21005968 is about 4583.2268108834. The cubic root of 21005968 is about 275.9185504952.

The spelling of 21005968 in words is "twenty-one million, five thousand, nine hundred sixty-eight".