21064709 has 4 divisors (see below), whose sum is σ = 21218604. Its totient is φ = 20910816.

The previous prime is 21064679. The next prime is 21064723. The reversal of 21064709 is 90746012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15760900 + 5303809 = 3970^2 + 2303^2 .

It is a cyclic number.

It is not a de Polignac number, because 21064709 - 2²⁰ = 20016133 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21064009) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76742 + ... + 77015.

It is an arithmetic number, because the mean of its divisors is an integer number (5304651).

Almost surely, 2^21064709 is an apocalyptic number.

It is an amenable number.

21064709 is a deficient number, since it is larger than the sum of its proper divisors (153895).

21064709 is a wasteful number, since it uses less digits than its factorization.

21064709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153894.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 21064709 is about 4589.6305951569. The cubic root of 21064709 is about 276.1755036185.

The spelling of 21064709 in words is "twenty-one million, sixty-four thousand, seven hundred nine".