645973 has 2 divisors, whose sum is σ = 645974. Its totient is φ = 645972.

The previous prime is 645941. The next prime is 645979. The reversal of 645973 is 379546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 357604 + 288369 = 598^2 + 537^2 .

It is a cyclic number.

It is not a de Polignac number, because 645973 - 2⁵ = 645941 is a prime.

It is a super-2 number, since 2×645973² = 834562233458, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322986 + 322987.

It is an arithmetic number, because the mean of its divisors is an integer number (322987).

2⁶⁴⁵⁹⁷³ is an apocalyptic number.

It is an amenable number.

645973 is a deficient number, since it is larger than the sum of its proper divisors (1).

645973 is an equidigital number, since it uses as much as digits as its factorization.

645973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 34.

The square root of 645973 is about 803.7244552706. The cubic root of 645973 is about 86.4446503467. Note that the first 3 decimals are identical.

The spelling of 645973 in words is "six hundred forty-five thousand, nine hundred seventy-three".