661207321 has 2 divisors, whose sum is σ = 661207322. Its totient is φ = 661207320.

The previous prime is 661207319. The next prime is 661207343. The reversal of 661207321 is 123702166.

661207321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 613057600 + 48149721 = 24760^2 + 6939^2 .

It is a cyclic number.

It is not a de Polignac number, because 661207321 - 2¹ = 661207319 is a prime.

Together with 661207319, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 661207321.

It is not a weakly prime, because it can be changed into another prime (661208321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330603660 + 330603661.

It is an arithmetic number, because the mean of its divisors is an integer number (330603661).

Almost surely, 2^661207321 is an apocalyptic number.

It is an amenable number.

661207321 is a deficient number, since it is larger than the sum of its proper divisors (1).

661207321 is an equidigital number, since it uses as much as digits as its factorization.

661207321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 661207321 is about 25713.9518744202. The cubic root of 661207321 is about 871.1893369508.

Adding to 661207321 its reverse (123702166), we get a palindrome (784909487).

It can be divided in two parts, 66120 and 7321, that added together give a square (73441 = 271²).

The spelling of 661207321 in words is "six hundred sixty-one million, two hundred seven thousand, three hundred twenty-one".