645865949 has 2 divisors, whose sum is σ = 645865950. Its totient is φ = 645865948.

The previous prime is 645865943. The next prime is 645865951. The reversal of 645865949 is 949568546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 643636900 + 2229049 = 25370^2 + 1493^2 .

It is a cyclic number.

It is not a de Polignac number, because 645865949 - 2⁴ = 645865933 is a prime.

Together with 645865951, 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 = 645865894 and 645865903.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645865943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322932974 + 322932975.

It is an arithmetic number, because the mean of its divisors is an integer number (322932975).

Almost surely, 2^645865949 is an apocalyptic number.

It is an amenable number.

645865949 is a deficient number, since it is larger than the sum of its proper divisors (1).

645865949 is an equidigital number, since it uses as much as digits as its factorization.

645865949 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9331200, while the sum is 56.

The square root of 645865949 is about 25413.8928344321. The cubic root of 645865949 is about 864.3987486458.

The spelling of 645865949 in words is "six hundred forty-five million, eight hundred sixty-five thousand, nine hundred forty-nine".