645438749 has 2 divisors, whose sum is σ = 645438750. Its totient is φ = 645438748.

The previous prime is 645438727. The next prime is 645438751. The reversal of 645438749 is 947834546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 641608900 + 3829849 = 25330^2 + 1957^2 .

It is a cyclic number.

It is not a de Polignac number, because 645438749 - 2²⁸ = 377003293 is a prime.

Together with 645438751, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 645438697 and 645438706.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645438709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322719374 + 322719375.

It is an arithmetic number, because the mean of its divisors is an integer number (322719375).

Almost surely, 2^645438749 is an apocalyptic number.

It is an amenable number.

645438749 is a deficient number, since it is larger than the sum of its proper divisors (1).

645438749 is an equidigital number, since it uses as much as digits as its factorization.

645438749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2903040, while the sum is 50.

The square root of 645438749 is about 25405.4865924666. The cubic root of 645438749 is about 864.2081246768.

The spelling of 645438749 in words is "six hundred forty-five million, four hundred thirty-eight thousand, seven hundred forty-nine".