21005704 has 16 divisors (see below), whose sum is σ = 39455820. Its totient is φ = 10484160.

The previous prime is 21005701. The next prime is 21005707. The reversal of 21005704 is 40750012.

It is an interprime number because it is at equal distance from previous prime (21005701) and next prime (21005707).

It can be written as a sum of positive squares in 2 ways, for example, as 17656804 + 3348900 = 4202^2 + 1830^2 .

It is not an unprimeable number, because it can be changed into a prime (21005701) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 3214 + ... + 7234.

Almost surely, 2^21005704 is an apocalyptic number.

It is an amenable number.

21005704 is a deficient number, since it is larger than the sum of its proper divisors (18450116).

21005704 is a wasteful number, since it uses less digits than its factorization.

21005704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4680 (or 4676 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 21005704 is about 4583.1980101235. The cubic root of 21005704 is about 275.9173945888.

Adding to 21005704 its reverse (40750012), we get a palindrome (61755716).

The spelling of 21005704 in words is "twenty-one million, five thousand, seven hundred four".