55121221621 has 2 divisors, whose sum is σ = 55121221622. Its totient is φ = 55121221620.

The previous prime is 55121221567. The next prime is 55121221637. The reversal of 55121221621 is 12612212155.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 55119300625 + 1920996 = 234775^2 + 1386^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-55121221621 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 55121221621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (55121221721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27560610810 + 27560610811.

It is an arithmetic number, because the mean of its divisors is an integer number (27560610811).

Almost surely, 2^55121221621 is an apocalyptic number.

It is an amenable number.

55121221621 is a deficient number, since it is larger than the sum of its proper divisors (1).

55121221621 is an equidigital number, since it uses as much as digits as its factorization.

55121221621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2400, while the sum is 28.

Adding to 55121221621 its reverse (12612212155), we get a palindrome (67733433776).

The spelling of 55121221621 in words is "fifty-five billion, one hundred twenty-one million, two hundred twenty-one thousand, six hundred twenty-one".