21122561777 has 2 divisors, whose sum is σ = 21122561778. Its totient is φ = 21122561776.

The previous prime is 21122561767. The next prime is 21122561807. The reversal of 21122561777 is 77716522112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18116890801 + 3005670976 = 134599^2 + 54824^2 .

It is a cyclic number.

It is not a de Polignac number, because 21122561777 - 2³⁰ = 20048819953 is a prime.

It is not a weakly prime, because it can be changed into another prime (21122561737) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561280888 + 10561280889.

It is an arithmetic number, because the mean of its divisors is an integer number (10561280889).

Almost surely, 2^21122561777 is an apocalyptic number.

It is an amenable number.

21122561777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21122561777 is an equidigital number, since it uses as much as digits as its factorization.

21122561777 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82320, while the sum is 41.

The spelling of 21122561777 in words is "twenty-one billion, one hundred twenty-two million, five hundred sixty-one thousand, seven hundred seventy-seven".