645857609 has 2 divisors, whose sum is σ = 645857610. Its totient is φ = 645857608.

The previous prime is 645857599. The next prime is 645857617. The reversal of 645857609 is 906758546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 613651984 + 32205625 = 24772^2 + 5675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645857609 is a prime.

It is a super-2 number, since 2×645857609² = 834264102206393762, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (645857699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322928804 + 322928805.

It is an arithmetic number, because the mean of its divisors is an integer number (322928805).

Almost surely, 2^645857609 is an apocalyptic number.

It is an amenable number.

645857609 is a deficient number, since it is larger than the sum of its proper divisors (1).

645857609 is an equidigital number, since it uses as much as digits as its factorization.

645857609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1814400, while the sum is 50.

The square root of 645857609 is about 25413.7287504215. The cubic root of 645857609 is about 864.3950279994.

The spelling of 645857609 in words is "six hundred forty-five million, eight hundred fifty-seven thousand, six hundred nine".