20640044693 has 2 divisors, whose sum is σ = 20640044694. Its totient is φ = 20640044692.

The previous prime is 20640044669. The next prime is 20640044701. The reversal of 20640044693 is 39644004602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19203862084 + 1436182609 = 138578^2 + 37897^2 .

It is a cyclic number.

It is not a de Polignac number, because 20640044693 - 2²⁶ = 20572935829 is a prime.

It is a super-2 number, since 2×20640044693² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20640044393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10320022346 + 10320022347.

It is an arithmetic number, because the mean of its divisors is an integer number (10320022347).

Almost surely, 2^20640044693 is an apocalyptic number.

It is an amenable number.

20640044693 is a deficient number, since it is larger than the sum of its proper divisors (1).

20640044693 is an equidigital number, since it uses as much as digits as its factorization.

20640044693 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 124416, while the sum is 38.

The spelling of 20640044693 in words is "twenty billion, six hundred forty million, forty-four thousand, six hundred ninety-three".