20665709 has 4 divisors (see below), whose sum is σ = 20802720. Its totient is φ = 20528700.

The previous prime is 20665669. The next prime is 20665739. The reversal of 20665709 is 90756602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20665709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20665739) 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, 68279 + ... + 68580.

It is an arithmetic number, because the mean of its divisors is an integer number (5200680).

Almost surely, 2^20665709 is an apocalyptic number.

It is an amenable number.

20665709 is a deficient number, since it is larger than the sum of its proper divisors (137011).

20665709 is a wasteful number, since it uses less digits than its factorization.

20665709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137010.

The product of its (nonzero) digits is 22680, while the sum is 35.

The square root of 20665709 is about 4545.9552351514. The cubic root of 20665709 is about 274.4206381259.

The spelling of 20665709 in words is "twenty million, six hundred sixty-five thousand, seven hundred nine".