661961 has 2 divisors, whose sum is σ = 661962. Its totient is φ = 661960.

The previous prime is 661951. The next prime is 661987. The reversal of 661961 is 169166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 366025 + 295936 = 605^2 + 544^2 .

It is a cyclic number.

It is not a de Polignac number, because 661961 - 2⁶ = 661897 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a plaindrome in base 14.

It is not a weakly prime, because it can be changed into another prime (661931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330980 + 330981.

It is an arithmetic number, because the mean of its divisors is an integer number (330981).

2⁶⁶¹⁹⁶¹ is an apocalyptic number.

It is an amenable number.

661961 is a deficient number, since it is larger than the sum of its proper divisors (1).

661961 is an equidigital number, since it uses as much as digits as its factorization.

661961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1944, while the sum is 29.

The square root of 661961 is about 813.6098573641. The cubic root of 661961 is about 87.1520220458.

The spelling of 661961 in words is "six hundred sixty-one thousand, nine hundred sixty-one".