21655546550321 has 2 divisors, whose sum is σ = 21655546550322. Its totient is φ = 21655546550320.

The previous prime is 21655546550279. The next prime is 21655546550329. The reversal of 21655546550321 is 12305564555612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18443924140321 + 3211622410000 = 4294639^2 + 1792100^2 .

It is a cyclic number.

It is not a de Polignac number, because 21655546550321 - 2¹⁰ = 21655546549297 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21655546550321.

It is not a weakly prime, because it can be changed into another prime (21655546550329) 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, 10827773275160 + 10827773275161.

It is an arithmetic number, because the mean of its divisors is an integer number (10827773275161).

Almost surely, 2^{21655546550321} is an apocalyptic number.

It is an amenable number.

21655546550321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655546550321 is an equidigital number, since it uses as much as digits as its factorization.

21655546550321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5400000, while the sum is 50.

The spelling of 21655546550321 in words is "twenty-one trillion, six hundred fifty-five billion, five hundred forty-six million, five hundred fifty thousand, three hundred twenty-one".