20999761564777 has 2 divisors, whose sum is σ = 20999761564778. Its totient is φ = 20999761564776.

The previous prime is 20999761564723. The next prime is 20999761564807. The reversal of 20999761564777 is 77746516799902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16267500823401 + 4732260741376 = 4033299^2 + 2175376^2 .

It is a cyclic number.

It is not a de Polignac number, because 20999761564777 - 2³⁵ = 20965401826409 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20999761564697 and 20999761564706.

It is not a weakly prime, because it can be changed into another prime (20999761562777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10499880782388 + 10499880782389.

It is an arithmetic number, because the mean of its divisors is an integer number (10499880782389).

Almost surely, 2^{20999761564777} is an apocalyptic number.

It is an amenable number.

20999761564777 is a deficient number, since it is larger than the sum of its proper divisors (1).

20999761564777 is an equidigital number, since it uses as much as digits as its factorization.

20999761564777 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520473760, while the sum is 79.

The spelling of 20999761564777 in words is "twenty trillion, nine hundred ninety-nine billion, seven hundred sixty-one million, five hundred sixty-four thousand, seven hundred seventy-seven".