661498309 has 2 divisors, whose sum is σ = 661498310. Its totient is φ = 661498308.

The previous prime is 661498307. The next prime is 661498379. The reversal of 661498309 is 903894166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 661004100 + 494209 = 25710^2 + 703^2 .

It is a cyclic number.

It is not a de Polignac number, because 661498309 - 2¹ = 661498307 is a prime.

Together with 661498307, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661498301) 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, 330749154 + 330749155.

It is an arithmetic number, because the mean of its divisors is an integer number (330749155).

Almost surely, 2^661498309 is an apocalyptic number.

It is an amenable number.

661498309 is a deficient number, since it is larger than the sum of its proper divisors (1).

661498309 is an equidigital number, since it uses as much as digits as its factorization.

661498309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 279936, while the sum is 46.

The square root of 661498309 is about 25719.6094254948. The cubic root of 661498309 is about 871.3171175807.

The spelling of 661498309 in words is "six hundred sixty-one million, four hundred ninety-eight thousand, three hundred nine".