11555771621 has 2 divisors, whose sum is σ = 11555771622. Its totient is φ = 11555771620.

The previous prime is 11555771611. The next prime is 11555771653. The reversal of 11555771621 is 12617755511.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6906441025 + 4649330596 = 83105^2 + 68186^2 .

It is a cyclic number.

It is not a de Polignac number, because 11555771621 - 2¹⁸ = 11555509477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11555771611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5777885810 + 5777885811.

It is an arithmetic number, because the mean of its divisors is an integer number (5777885811).

Almost surely, 2^11555771621 is an apocalyptic number.

It is an amenable number.

11555771621 is a deficient number, since it is larger than the sum of its proper divisors (1).

11555771621 is an equidigital number, since it uses as much as digits as its factorization.

11555771621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 73500, while the sum is 41.

The spelling of 11555771621 in words is "eleven billion, five hundred fifty-five million, seven hundred seventy-one thousand, six hundred twenty-one".