1665000061561 has 2 divisors, whose sum is σ = 1665000061562. Its totient is φ = 1665000061560.

The previous prime is 1665000061471. The next prime is 1665000061601. The reversal of 1665000061561 is 1651600005661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1507355329536 + 157644732025 = 1227744^2 + 397045^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665000061561 - 2⁷ = 1665000061433 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1665000061561.

It is not a weakly prime, because it can be changed into another prime (1665000061861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832500030780 + 832500030781.

It is an arithmetic number, because the mean of its divisors is an integer number (832500030781).

Almost surely, 2^{1665000061561} is an apocalyptic number.

It is an amenable number.

1665000061561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665000061561 is an equidigital number, since it uses as much as digits as its factorization.

1665000061561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32400, while the sum is 37.

The spelling of 1665000061561 in words is "one trillion, six hundred sixty-five billion, sixty-one thousand, five hundred sixty-one".