207561661 has 2 divisors, whose sum is σ = 207561662. Its totient is φ = 207561660.

The previous prime is 207561623. The next prime is 207561691. The reversal of 207561661 is 166165702.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 204776100 + 2785561 = 14310^2 + 1669^2 .

It is a cyclic number.

It is not a de Polignac number, because 207561661 - 2¹⁷ = 207430589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (207561691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103780830 + 103780831.

It is an arithmetic number, because the mean of its divisors is an integer number (103780831).

Almost surely, 2^207561661 is an apocalyptic number.

It is an amenable number.

207561661 is a deficient number, since it is larger than the sum of its proper divisors (1).

207561661 is an equidigital number, since it uses as much as digits as its factorization.

207561661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 207561661 is about 14407.0004164642. Note that the first 3 decimals coincide. The cubic root of 207561661 is about 592.0827102069.

It can be divided in two parts, 2075 and 61661, that added together give a palindrome (63736).

The spelling of 207561661 in words is "two hundred seven million, five hundred sixty-one thousand, six hundred sixty-one".