21556546447 has 2 divisors, whose sum is σ = 21556546448. Its totient is φ = 21556546446.

The previous prime is 21556546399. The next prime is 21556546513. The reversal of 21556546447 is 74464565512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21556546447 is a prime.

It is a super-3 number, since 3×21556546447³ (a number of 32 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21556546447.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21556549447) 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, 10778273223 + 10778273224.

It is an arithmetic number, because the mean of its divisors is an integer number (10778273224).

Almost surely, 2^21556546447 is an apocalyptic number.

21556546447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21556546447 is an equidigital number, since it uses as much as digits as its factorization.

21556546447 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032000, while the sum is 49.

The spelling of 21556546447 in words is "twenty-one billion, five hundred fifty-six million, five hundred forty-six thousand, four hundred forty-seven".