20639569 has 2 divisors, whose sum is σ = 20639570. Its totient is φ = 20639568.

The previous prime is 20639539. The next prime is 20639573. The reversal of 20639569 is 96593602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19228225 + 1411344 = 4385^2 + 1188^2 .

It is a cyclic number.

It is not a de Polignac number, because 20639569 - 2⁹ = 20639057 is a prime.

It is a super-2 number, since 2×20639569² = 851983617011522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20639519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10319784 + 10319785.

It is an arithmetic number, because the mean of its divisors is an integer number (10319785).

Almost surely, 2^20639569 is an apocalyptic number.

It is an amenable number.

20639569 is a deficient number, since it is larger than the sum of its proper divisors (1).

20639569 is an equidigital number, since it uses as much as digits as its factorization.

20639569 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 87480, while the sum is 40.

The square root of 20639569 is about 4543.0792421000. The cubic root of 20639569 is about 274.3048846632.

The spelling of 20639569 in words is "twenty million, six hundred thirty-nine thousand, five hundred sixty-nine".