21310556549 has 2 divisors, whose sum is σ = 21310556550. Its totient is φ = 21310556548.

The previous prime is 21310556543. The next prime is 21310556581. The reversal of 21310556549 is 94565501312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19816192900 + 1494363649 = 140770^2 + 38657^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21310556549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21310556543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655278274 + 10655278275.

It is an arithmetic number, because the mean of its divisors is an integer number (10655278275).

Almost surely, 2^21310556549 is an apocalyptic number.

It is an amenable number.

21310556549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21310556549 is an equidigital number, since it uses as much as digits as its factorization.

21310556549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162000, while the sum is 41.

The spelling of 21310556549 in words is "twenty-one billion, three hundred ten million, five hundred fifty-six thousand, five hundred forty-nine".