669721601 has 2 divisors, whose sum is σ = 669721602. Its totient is φ = 669721600.

The previous prime is 669721597. The next prime is 669721609. The reversal of 669721601 is 106127966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 369600625 + 300120976 = 19225^2 + 17324^2 .

It is a cyclic number.

It is not a de Polignac number, because 669721601 - 2² = 669721597 is a prime.

It is not a weakly prime, because it can be changed into another prime (669721609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334860800 + 334860801.

It is an arithmetic number, because the mean of its divisors is an integer number (334860801).

Almost surely, 2^669721601 is an apocalyptic number.

It is an amenable number.

669721601 is a deficient number, since it is larger than the sum of its proper divisors (1).

669721601 is an equidigital number, since it uses as much as digits as its factorization.

669721601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 669721601 is about 25878.9799064801. The cubic root of 669721601 is about 874.9127971872.

The spelling of 669721601 in words is "six hundred sixty-nine million, seven hundred twenty-one thousand, six hundred one".