20551709 has 4 divisors (see below), whose sum is σ = 20572860. Its totient is φ = 20530560.

The previous prime is 20551703. The next prime is 20551733. The reversal of 20551709 is 90715502.

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 15578809 + 4972900 = 3947^2 + 2230^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20551709 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 (20551703) 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, 9044 + ... + 11085.

It is an arithmetic number, because the mean of its divisors is an integer number (5143215).

Almost surely, 2^20551709 is an apocalyptic number.

It is an amenable number.

20551709 is a deficient number, since it is larger than the sum of its proper divisors (21151).

20551709 is a wasteful number, since it uses less digits than its factorization.

20551709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21150.

The product of its (nonzero) digits is 3150, while the sum is 29.

The square root of 20551709 is about 4533.3992764812. The cubic root of 20551709 is about 273.9151041443.

The spelling of 20551709 in words is "twenty million, five hundred fifty-one thousand, seven hundred nine".