661691599 has 2 divisors, whose sum is σ = 661691600. Its totient is φ = 661691598.

The previous prime is 661691573. The next prime is 661691603. The reversal of 661691599 is 995196166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661691599 - 2¹¹ = 661689551 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661691509) 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, 330845799 + 330845800.

It is an arithmetic number, because the mean of its divisors is an integer number (330845800).

Almost surely, 2^661691599 is an apocalyptic number.

661691599 is a deficient number, since it is larger than the sum of its proper divisors (1).

661691599 is an equidigital number, since it uses as much as digits as its factorization.

661691599 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 787320, while the sum is 52.

The square root of 661691599 is about 25723.3667897497. The cubic root of 661691599 is about 871.4019756885.

The spelling of 661691599 in words is "six hundred sixty-one million, six hundred ninety-one thousand, five hundred ninety-nine".