645409 has 2 divisors, whose sum is σ = 645410. Its totient is φ = 645408.

The previous prime is 645397. The next prime is 645419. The reversal of 645409 is 904546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 567009 + 78400 = 753^2 + 280^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645409 is a prime.

It is not a weakly prime, because it can be changed into another prime (645419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322704 + 322705.

It is an arithmetic number, because the mean of its divisors is an integer number (322705).

2⁶⁴⁵⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

645409 is a deficient number, since it is larger than the sum of its proper divisors (1).

645409 is an equidigital number, since it uses as much as digits as its factorization.

645409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 645409 is about 803.3735121349. The cubic root of 645409 is about 86.4194847030.

The spelling of 645409 in words is "six hundred forty-five thousand, four hundred nine".