21003993 has 24 divisors (see below), whose sum is σ = 32449248. Its totient is φ = 13045632.

The previous prime is 21003937. The next prime is 21004043. The reversal of 21003993 is 39930012.

It is not a de Polignac number, because 21003993 - 2⁶ = 21003929 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21003293) by changing a digit.

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 in 23 ways as a sum of consecutive naturals, for example, 15730 + ... + 17012.

It is an arithmetic number, because the mean of its divisors is an integer number (1352052).

Almost surely, 2^21003993 is an apocalyptic number.

It is an amenable number.

21003993 is a deficient number, since it is larger than the sum of its proper divisors (11445255).

21003993 is a wasteful number, since it uses less digits than its factorization.

21003993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1413 (or 1410 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 27.

The square root of 21003993 is about 4583.0113462657. The cubic root of 21003993 is about 275.9099028541.

The spelling of 21003993 in words is "twenty-one million, three thousand, nine hundred ninety-three".