3661561 has 2 divisors, whose sum is σ = 3661562. Its totient is φ = 3661560.

The previous prime is 3661543. The next prime is 3661573. The reversal of 3661561 is 1651663.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2621161 + 1040400 = 1619^2 + 1020^2 .

It is a cyclic number.

It is not a de Polignac number, because 3661561 - 2⁵ = 3661529 is a prime.

It is not a weakly prime, because it can be changed into another prime (3661501) 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, 1830780 + 1830781.

It is an arithmetic number, because the mean of its divisors is an integer number (1830781).

Almost surely, 2^3661561 is an apocalyptic number.

It is an amenable number.

3661561 is a deficient number, since it is larger than the sum of its proper divisors (1).

3661561 is an equidigital number, since it uses as much as digits as its factorization.

3661561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 28.

The square root of 3661561 is about 1913.5205773652. The cubic root of 3661561 is about 154.1305605568.

The spelling of 3661561 in words is "three million, six hundred sixty-one thousand, five hundred sixty-one".