645604261 has 2 divisors, whose sum is σ = 645604262. Its totient is φ = 645604260.

The previous prime is 645604241. The next prime is 645604283. The reversal of 645604261 is 162406546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 535228225 + 110376036 = 23135^2 + 10506^2 .

It is a cyclic number.

It is not a de Polignac number, because 645604261 - 2⁵ = 645604229 is a prime.

It is a super-2 number, since 2×645604261² = 833609723642712242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645604241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322802130 + 322802131.

It is an arithmetic number, because the mean of its divisors is an integer number (322802131).

Almost surely, 2^645604261 is an apocalyptic number.

It is an amenable number.

645604261 is a deficient number, since it is larger than the sum of its proper divisors (1).

645604261 is an equidigital number, since it uses as much as digits as its factorization.

645604261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 645604261 is about 25408.7437902782. The cubic root of 645604261 is about 864.2819889490.

The spelling of 645604261 in words is "six hundred forty-five million, six hundred four thousand, two hundred sixty-one".