2021557066561 has 2 divisors, whose sum is σ = 2021557066562. Its totient is φ = 2021557066560.

The previous prime is 2021557066549. The next prime is 2021557066567. The reversal of 2021557066561 is 1656607551202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1282060262961 + 739496803600 = 1132281^2 + 859940^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021557066561 - 2¹⁹ = 2021556542273 is a prime.

It is not a weakly prime, because it can be changed into another prime (2021557066567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1010778533280 + 1010778533281.

It is an arithmetic number, because the mean of its divisors is an integer number (1010778533281).

Almost surely, 2^{2021557066561} is an apocalyptic number.

It is an amenable number.

2021557066561 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021557066561 is an equidigital number, since it uses as much as digits as its factorization.

2021557066561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 756000, while the sum is 46.

The spelling of 2021557066561 in words is "two trillion, twenty-one billion, five hundred fifty-seven million, sixty-six thousand, five hundred sixty-one".