20661751217 has 2 divisors, whose sum is σ = 20661751218. Its totient is φ = 20661751216.

The previous prime is 20661751177. The next prime is 20661751247. The reversal of 20661751217 is 71215716602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19310159521 + 1351591696 = 138961^2 + 36764^2 .

It is a cyclic number.

It is not a de Polignac number, because 20661751217 - 2⁸ = 20661750961 is a prime.

It is not a weakly prime, because it can be changed into another prime (20661751247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10330875608 + 10330875609.

It is an arithmetic number, because the mean of its divisors is an integer number (10330875609).

Almost surely, 2^20661751217 is an apocalyptic number.

It is an amenable number.

20661751217 is a deficient number, since it is larger than the sum of its proper divisors (1).

20661751217 is an equidigital number, since it uses as much as digits as its factorization.

20661751217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 35280, while the sum is 38.

The spelling of 20661751217 in words is "twenty billion, six hundred sixty-one million, seven hundred fifty-one thousand, two hundred seventeen".