1661500591 has 2 divisors, whose sum is σ = 1661500592. Its totient is φ = 1661500590.

The previous prime is 1661500573. The next prime is 1661500609. The reversal of 1661500591 is 1950051661.

It is a balanced prime because it is at equal distance from previous prime (1661500573) and next prime (1661500609).

It is a cyclic number.

It is not a de Polignac number, because 1661500591 - 2²⁷ = 1527282863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661500531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830750295 + 830750296.

It is an arithmetic number, because the mean of its divisors is an integer number (830750296).

Almost surely, 2^1661500591 is an apocalyptic number.

1661500591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661500591 is an equidigital number, since it uses as much as digits as its factorization.

1661500591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8100, while the sum is 34.

The square root of 1661500591 is about 40761.5086938646. The cubic root of 1661500591 is about 1184.4048216151.

The spelling of 1661500591 in words is "one billion, six hundred sixty-one million, five hundred thousand, five hundred ninety-one".