661780099 has 2 divisors, whose sum is σ = 661780100. Its totient is φ = 661780098.

The previous prime is 661780079. The next prime is 661780117. The reversal of 661780099 is 990087166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661780099 - 2¹⁹ = 661255811 is a prime.

It is not a weakly prime, because it can be changed into another prime (661780079) 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, 330890049 + 330890050.

It is an arithmetic number, because the mean of its divisors is an integer number (330890050).

Almost surely, 2^661780099 is an apocalyptic number.

661780099 is a deficient number, since it is larger than the sum of its proper divisors (1).

661780099 is an equidigital number, since it uses as much as digits as its factorization.

661780099 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 163296, while the sum is 46.

The square root of 661780099 is about 25725.0869580649. The cubic root of 661780099 is about 871.4408234120.

The spelling of 661780099 in words is "six hundred sixty-one million, seven hundred eighty thousand, ninety-nine".