645865951 has 2 divisors, whose sum is σ = 645865952. Its totient is φ = 645865950.

The previous prime is 645865949. The next prime is 645866009. The reversal of 645865951 is 159568546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645865951 - 2¹ = 645865949 is a prime.

It is a super-2 number, since 2×645865951² = 834285653322268802, which contains 22 as substring.

Together with 645865949, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 645865895 and 645865904.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645865151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322932975 + 322932976.

It is an arithmetic number, because the mean of its divisors is an integer number (322932976).

Almost surely, 2^645865951 is an apocalyptic number.

645865951 is a deficient number, since it is larger than the sum of its proper divisors (1).

645865951 is an equidigital number, since it uses as much as digits as its factorization.

645865951 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296000, while the sum is 49.

The square root of 645865951 is about 25413.8928737807. The cubic root of 645865951 is about 864.3987495381.

The spelling of 645865951 in words is "six hundred forty-five million, eight hundred sixty-five thousand, nine hundred fifty-one".