1661807591 has 2 divisors, whose sum is σ = 1661807592. Its totient is φ = 1661807590.

The previous prime is 1661807557. The next prime is 1661807593. The reversal of 1661807591 is 1957081661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1661807591 - 2¹⁴ = 1661791207 is a prime.

Together with 1661807593, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661807593) 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, 830903795 + 830903796.

It is an arithmetic number, because the mean of its divisors is an integer number (830903796).

Almost surely, 2^1661807591 is an apocalyptic number.

1661807591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661807591 is an equidigital number, since it uses as much as digits as its factorization.

1661807591 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90720, while the sum is 44.

The square root of 1661807591 is about 40765.2743275450. The cubic root of 1661807591 is about 1184.4777656933.

The spelling of 1661807591 in words is "one billion, six hundred sixty-one million, eight hundred seven thousand, five hundred ninety-one".