21000807 has 12 divisors (see below), whose sum is σ = 30719520. Its totient is φ = 13822848.

The previous prime is 21000803. The next prime is 21000821. The reversal of 21000807 is 70800012.

It is not a de Polignac number, because 21000807 - 2² = 21000803 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21000807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14058 + ... + 15479.

It is an arithmetic number, because the mean of its divisors is an integer number (2559960).

Almost surely, 2^21000807 is an apocalyptic number.

21000807 is a deficient number, since it is larger than the sum of its proper divisors (9718713).

21000807 is a wasteful number, since it uses less digits than its factorization.

21000807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29622 (or 29619 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21000807 is about 4582.6637450286. The cubic root of 21000807 is about 275.8959516433.

Adding to 21000807 its reverse (70800012), we get a palindrome (91800819).

The spelling of 21000807 in words is "twenty-one million, eight hundred seven", and thus it is an aban number.