20809669 has 2 divisors, whose sum is σ = 20809670. Its totient is φ = 20809668.

The previous prime is 20809667. The next prime is 20809699. The reversal of 20809669 is 96690802.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20593444 + 216225 = 4538^2 + 465^2 .

It is a cyclic number.

It is not a de Polignac number, because 20809669 - 2¹ = 20809667 is a prime.

It is a super-2 number, since 2×20809669² = 866084647779122, which contains 22 as substring.

Together with 20809667, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20809667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10404834 + 10404835.

It is an arithmetic number, because the mean of its divisors is an integer number (10404835).

Almost surely, 2^20809669 is an apocalyptic number.

It is an amenable number.

20809669 is a deficient number, since it is larger than the sum of its proper divisors (1).

20809669 is an equidigital number, since it uses as much as digits as its factorization.

20809669 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 40.

The square root of 20809669 is about 4561.7616114830. The cubic root of 20809669 is about 275.0563807265.

The spelling of 20809669 in words is "twenty million, eight hundred nine thousand, six hundred sixty-nine".