20644540717 has 2 divisors, whose sum is σ = 20644540718. Its totient is φ = 20644540716.

The previous prime is 20644540667. The next prime is 20644540729. The reversal of 20644540717 is 71704544602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17559960196 + 3084580521 = 132514^2 + 55539^2 .

It is a cyclic number.

It is not a de Polignac number, because 20644540717 - 2⁷ = 20644540589 is a prime.

It is a super-2 number, since 2×20644540717² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20644540717.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20644540747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10322270358 + 10322270359.

It is an arithmetic number, because the mean of its divisors is an integer number (10322270359).

Almost surely, 2^20644540717 is an apocalyptic number.

It is an amenable number.

20644540717 is a deficient number, since it is larger than the sum of its proper divisors (1).

20644540717 is an equidigital number, since it uses as much as digits as its factorization.

20644540717 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 188160, while the sum is 40.

The spelling of 20644540717 in words is "twenty billion, six hundred forty-four million, five hundred forty thousand, seven hundred seventeen".