661217 has 2 divisors, whose sum is σ = 661218. Its totient is φ = 661216.

The previous prime is 661201. The next prime is 661231. The reversal of 661217 is 712166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 519841 + 141376 = 721^2 + 376^2 .

It is a cyclic number.

It is not a de Polignac number, because 661217 - 2⁴ = 661201 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 661192 and 661201.

It is not a weakly prime, because it can be changed into another prime (661237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330608 + 330609.

It is an arithmetic number, because the mean of its divisors is an integer number (330609).

2⁶⁶¹²¹⁷ is an apocalyptic number.

It is an amenable number.

661217 is a deficient number, since it is larger than the sum of its proper divisors (1).

661217 is an equidigital number, since it uses as much as digits as its factorization.

661217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 504, while the sum is 23.

The square root of 661217 is about 813.1525072211. The cubic root of 661217 is about 87.1193587862.

It can be divided in two parts, 661 and 217, that added together give a palindrome (878).

The spelling of 661217 in words is "six hundred sixty-one thousand, two hundred seventeen".