21655615771 has 2 divisors, whose sum is σ = 21655615772. Its totient is φ = 21655615770.

The previous prime is 21655615763. The next prime is 21655615829. The reversal of 21655615771 is 17751655612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21655615771 - 2³ = 21655615763 is a prime.

It is not a weakly prime, because it can be changed into another prime (21655615741) 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, 10827807885 + 10827807886.

It is an arithmetic number, because the mean of its divisors is an integer number (10827807886).

Almost surely, 2^21655615771 is an apocalyptic number.

21655615771 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655615771 is an equidigital number, since it uses as much as digits as its factorization.

21655615771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 441000, while the sum is 46.

The spelling of 21655615771 in words is "twenty-one billion, six hundred fifty-five million, six hundred fifteen thousand, seven hundred seventy-one".