661909393 has 2 divisors, whose sum is σ = 661909394. Its totient is φ = 661909392.

The previous prime is 661909361. The next prime is 661909397. The reversal of 661909393 is 393909166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 388602369 + 273307024 = 19713^2 + 16532^2 .

It is a cyclic number.

It is not a de Polignac number, because 661909393 - 2⁵ = 661909361 is a prime.

It is not a weakly prime, because it can be changed into another prime (661909397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330954696 + 330954697.

It is an arithmetic number, because the mean of its divisors is an integer number (330954697).

Almost surely, 2^661909393 is an apocalyptic number.

It is an amenable number.

661909393 is a deficient number, since it is larger than the sum of its proper divisors (1).

661909393 is an equidigital number, since it uses as much as digits as its factorization.

661909393 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 236196, while the sum is 46.

The square root of 661909393 is about 25727.5998297548. The cubic root of 661909393 is about 871.4975717353.

The spelling of 661909393 in words is "six hundred sixty-one million, nine hundred nine thousand, three hundred ninety-three".