21556604543 has 2 divisors, whose sum is σ = 21556604544. Its totient is φ = 21556604542.

The previous prime is 21556604507. The next prime is 21556604557. The reversal of 21556604543 is 34540665512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21556604543 - 2²⁴ = 21539827327 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21556604543.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21556604143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10778302271 + 10778302272.

It is an arithmetic number, because the mean of its divisors is an integer number (10778302272).

Almost surely, 2^21556604543 is an apocalyptic number.

21556604543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21556604543 is an equidigital number, since it uses as much as digits as its factorization.

21556604543 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432000, while the sum is 41.

The spelling of 21556604543 in words is "twenty-one billion, five hundred fifty-six million, six hundred four thousand, five hundred forty-three".