21000689 has 2 divisors, whose sum is σ = 21000690. Its totient is φ = 21000688.

The previous prime is 21000677. The next prime is 21000709. The reversal of 21000689 is 98600012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20205025 + 795664 = 4495^2 + 892^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000689 - 2⁴ = 21000673 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21000589) 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 as a sum of consecutive naturals, namely, 10500344 + 10500345.

It is an arithmetic number, because the mean of its divisors is an integer number (10500345).

Almost surely, 2^21000689 is an apocalyptic number.

It is an amenable number.

21000689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000689 is an equidigital number, since it uses as much as digits as its factorization.

21000689 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21000689 is about 4582.6508704024. The cubic root of 21000689 is about 275.8954349047.

The spelling of 21000689 in words is "twenty-one million, six hundred eighty-nine", and thus it is an aban number.