21010609 has 2 divisors, whose sum is σ = 21010610. Its totient is φ = 21010608.

The previous prime is 21010601. The next prime is 21010663. The reversal of 21010609 is 90601012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14745600 + 6265009 = 3840^2 + 2503^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010609 - 2³ = 21010601 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21010601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505304 + 10505305.

It is an arithmetic number, because the mean of its divisors is an integer number (10505305).

Almost surely, 2^21010609 is an apocalyptic number.

It is an amenable number.

21010609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010609 is an equidigital number, since it uses as much as digits as its factorization.

21010609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21010609 is about 4583.7330855974. The cubic root of 21010609 is about 275.9388692240.

The spelling of 21010609 in words is "twenty-one million, ten thousand, six hundred nine".