1661125409 has 2 divisors, whose sum is σ = 1661125410. Its totient is φ = 1661125408.

The previous prime is 1661125357. The next prime is 1661125429. The reversal of 1661125409 is 9045211661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1656490000 + 4635409 = 40700^2 + 2153^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661125409 - 2⁸ = 1661125153 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1661125429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830562704 + 830562705.

It is an arithmetic number, because the mean of its divisors is an integer number (830562705).

Almost surely, 2^1661125409 is an apocalyptic number.

It is an amenable number.

1661125409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661125409 is an equidigital number, since it uses as much as digits as its factorization.

1661125409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 35.

The square root of 1661125409 is about 40756.9062736612. The cubic root of 1661125409 is about 1184.3156650972.

The spelling of 1661125409 in words is "one billion, six hundred sixty-one million, one hundred twenty-five thousand, four hundred nine".