2091918128821 has 2 divisors, whose sum is σ = 2091918128822. Its totient is φ = 2091918128820.

The previous prime is 2091918128777. The next prime is 2091918128849. The reversal of 2091918128821 is 1288218191902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1305166868721 + 786751260100 = 1142439^2 + 886990^2 .

It is a cyclic number.

It is not a de Polignac number, because 2091918128821 - 2⁷ = 2091918128693 is a prime.

It is a super-2 number, since 2×2091918128821² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2091918128891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1045959064410 + 1045959064411.

It is an arithmetic number, because the mean of its divisors is an integer number (1045959064411).

Almost surely, 2^{2091918128821} is an apocalyptic number.

It is an amenable number.

2091918128821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2091918128821 is an equidigital number, since it uses as much as digits as its factorization.

2091918128821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 331776, while the sum is 52.

The spelling of 2091918128821 in words is "two trillion, ninety-one billion, nine hundred eighteen million, one hundred twenty-eight thousand, eight hundred twenty-one".