645357253 has 6 divisors (see below), whose sum is σ = 674636774. Its totient is φ = 617297736.

The previous prime is 645357233. The next prime is 645357257. The reversal of 645357253 is 352753546.

It can be written as a sum of positive squares in only one way, i.e., 556865604 + 88491649 = 23598^2 + 9407^2 .

It is a de Polignac number, because none of the positive numbers 2^k-645357253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645357257) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 609450 + ... + 610507.

Almost surely, 2^645357253 is an apocalyptic number.

It is an amenable number.

645357253 is a deficient number, since it is larger than the sum of its proper divisors (29279521).

645357253 is a wasteful number, since it uses less digits than its factorization.

645357253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1220003 (or 1219980 counting only the distinct ones).

The product of its digits is 378000, while the sum is 40.

The square root of 645357253 is about 25403.8826363216. The cubic root of 645357253 is about 864.1717502107.

The spelling of 645357253 in words is "six hundred forty-five million, three hundred fifty-seven thousand, two hundred fifty-three".