661949 has 2 divisors, whose sum is σ = 661950. Its totient is φ = 661948.

The previous prime is 661939. The next prime is 661951. The reversal of 661949 is 949166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 648025 + 13924 = 805^2 + 118^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661949 is a prime.

It is a Sophie Germain prime.

Together with 661951, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330974 + 330975.

It is an arithmetic number, because the mean of its divisors is an integer number (330975).

2⁶⁶¹⁹⁴⁹ is an apocalyptic number.

It is an amenable number.

661949 is a deficient number, since it is larger than the sum of its proper divisors (1).

661949 is an equidigital number, since it uses as much as digits as its factorization.

661949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11664, while the sum is 35.

The square root of 661949 is about 813.6024827887. The cubic root of 661949 is about 87.1514954132.

The spelling of 661949 in words is "six hundred sixty-one thousand, nine hundred forty-nine".