21775564687 has 2 divisors, whose sum is σ = 21775564688. Its totient is φ = 21775564686.

The previous prime is 21775564607. The next prime is 21775564691. The reversal of 21775564687 is 78646557712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21775564687 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21775564607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10887782343 + 10887782344.

It is an arithmetic number, because the mean of its divisors is an integer number (10887782344).

Almost surely, 2^21775564687 is an apocalyptic number.

21775564687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21775564687 is an equidigital number, since it uses as much as digits as its factorization.

21775564687 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19756800, while the sum is 58.

The spelling of 21775564687 in words is "twenty-one billion, seven hundred seventy-five million, five hundred sixty-four thousand, six hundred eighty-seven".