645739 has 2 divisors, whose sum is σ = 645740. Its totient is φ = 645738.

The previous prime is 645737. The next prime is 645751. The reversal of 645739 is 937546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645739 - 2¹ = 645737 is a prime.

It is a super-2 number, since 2×645739² = 833957712242, which contains 22 as substring.

Together with 645737, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (645737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322869 + 322870.

It is an arithmetic number, because the mean of its divisors is an integer number (322870).

2⁶⁴⁵⁷³⁹ is an apocalyptic number.

645739 is a deficient number, since it is larger than the sum of its proper divisors (1).

645739 is an equidigital number, since it uses as much as digits as its factorization.

645739 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 645739 is about 803.5788698068. The cubic root of 645739 is about 86.4342110604.

The spelling of 645739 in words is "six hundred forty-five thousand, seven hundred thirty-nine".