20561976711421 has 2 divisors, whose sum is σ = 20561976711422. Its totient is φ = 20561976711420.

The previous prime is 20561976711347. The next prime is 20561976711491. The reversal of 20561976711421 is 12411767916502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16066669305625 + 4495307405796 = 4008325^2 + 2120214^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20561976711421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20561976711491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10280988355710 + 10280988355711.

It is an arithmetic number, because the mean of its divisors is an integer number (10280988355711).

Almost surely, 2^{20561976711421} is an apocalyptic number.

It is an amenable number.

20561976711421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20561976711421 is an equidigital number, since it uses as much as digits as its factorization.

20561976711421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1270080, while the sum is 52.

The spelling of 20561976711421 in words is "twenty trillion, five hundred sixty-one billion, nine hundred seventy-six million, seven hundred eleven thousand, four hundred twenty-one".