61661666011609 has 2 divisors, whose sum is σ = 61661666011610. Its totient is φ = 61661666011608.

The previous prime is 61661666011559. The next prime is 61661666011613. The reversal of 61661666011609 is 90611066616616.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56010300904009 + 5651365107600 = 7484003^2 + 2377260^2 .

It is a cyclic number.

It is not a de Polignac number, because 61661666011609 - 2⁷ = 61661666011481 is a prime.

It is a super-2 number, since 2×61661666011609² (a number of 28 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 61661666011609.

It is not a weakly prime, because it can be changed into another prime (61661666011619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30830833005804 + 30830833005805.

It is an arithmetic number, because the mean of its divisors is an integer number (30830833005805).

Almost surely, 2^{61661666011609} is an apocalyptic number.

It is an amenable number.

61661666011609 is a deficient number, since it is larger than the sum of its proper divisors (1).

61661666011609 is an equidigital number, since it uses as much as digits as its factorization.

61661666011609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2519424, while the sum is 55.

The spelling of 61661666011609 in words is "sixty-one trillion, six hundred sixty-one billion, six hundred sixty-six million, eleven thousand, six hundred nine".