21550784641 has 2 divisors, whose sum is σ = 21550784642. Its totient is φ = 21550784640.

The previous prime is 21550784639. The next prime is 21550784659. The reversal of 21550784641 is 14648705512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21227324416 + 323460225 = 145696^2 + 17985^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550784641 - 2¹ = 21550784639 is a prime.

It is a super-2 number, since 2×21550784641² (a number of 21 digits) contains 22 as substring.

Together with 21550784639, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21550784681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775392320 + 10775392321.

It is an arithmetic number, because the mean of its divisors is an integer number (10775392321).

Almost surely, 2^21550784641 is an apocalyptic number.

It is an amenable number.

21550784641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550784641 is an equidigital number, since it uses as much as digits as its factorization.

21550784641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 268800, while the sum is 43.

The spelling of 21550784641 in words is "twenty-one billion, five hundred fifty million, seven hundred eighty-four thousand, six hundred forty-one".