21011125549 has 2 divisors, whose sum is σ = 21011125550. Its totient is φ = 21011125548.

The previous prime is 21011125523. The next prime is 21011125567. The reversal of 21011125549 is 94552111012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17254661449 + 3756464100 = 131357^2 + 61290^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011125549 - 2¹¹ = 21011123501 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21011125549.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011125519) 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, 10505562774 + 10505562775.

It is an arithmetic number, because the mean of its divisors is an integer number (10505562775).

Almost surely, 2^21011125549 is an apocalyptic number.

It is an amenable number.

21011125549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011125549 is an equidigital number, since it uses as much as digits as its factorization.

21011125549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3600, while the sum is 31.

The spelling of 21011125549 in words is "twenty-one billion, eleven million, one hundred twenty-five thousand, five hundred forty-nine".