20561677757 has 2 divisors, whose sum is σ = 20561677758. Its totient is φ = 20561677756.

The previous prime is 20561677753. The next prime is 20561677781. The reversal of 20561677757 is 75777616502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20023948036 + 537729721 = 141506^2 + 23189^2 .

It is a cyclic number.

It is not a de Polignac number, because 20561677757 - 2² = 20561677753 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20561677699 and 20561677708.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20561677753) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10280838878 + 10280838879.

It is an arithmetic number, because the mean of its divisors is an integer number (10280838879).

Almost surely, 2^20561677757 is an apocalyptic number.

It is an amenable number.

20561677757 is a deficient number, since it is larger than the sum of its proper divisors (1).

20561677757 is an equidigital number, since it uses as much as digits as its factorization.

20561677757 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4321800, while the sum is 53.

The spelling of 20561677757 in words is "twenty billion, five hundred sixty-one million, six hundred seventy-seven thousand, seven hundred fifty-seven".