20669729 has 2 divisors, whose sum is σ = 20669730. Its totient is φ = 20669728.

The previous prime is 20669683. The next prime is 20669767. The reversal of 20669729 is 92796602.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16589329 + 4080400 = 4073^2 + 2020^2 .

It is a cyclic number.

It is not a de Polignac number, because 20669729 - 2²⁰ = 19621153 is a prime.

It is not a weakly prime, because it can be changed into another prime (20069729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10334864 + 10334865.

It is an arithmetic number, because the mean of its divisors is an integer number (10334865).

Almost surely, 2^20669729 is an apocalyptic number.

It is an amenable number.

20669729 is a deficient number, since it is larger than the sum of its proper divisors (1).

20669729 is an equidigital number, since it uses as much as digits as its factorization.

20669729 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81648, while the sum is 41.

The square root of 20669729 is about 4546.3973649473. The cubic root of 20669729 is about 274.4384308769.

The spelling of 20669729 in words is "twenty million, six hundred sixty-nine thousand, seven hundred twenty-nine".