645738751 has 4 divisors (see below), whose sum is σ = 737987152. Its totient is φ = 553490352.

The previous prime is 645738749. The next prime is 645738757. The reversal of 645738751 is 157837546.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 645738751 - 2¹ = 645738749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645738757) 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 in 3 ways as a sum of consecutive naturals, for example, 46124190 + ... + 46124203.

It is an arithmetic number, because the mean of its divisors is an integer number (184496788).

Almost surely, 2^645738751 is an apocalyptic number.

645738751 is a deficient number, since it is larger than the sum of its proper divisors (92248401).

645738751 is an equidigital number, since it uses as much as digits as its factorization.

645738751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92248400.

The product of its digits is 705600, while the sum is 46.

The square root of 645738751 is about 25411.3901823572. The cubic root of 645738751 is about 864.3419995062.

The spelling of 645738751 in words is "six hundred forty-five million, seven hundred thirty-eight thousand, seven hundred fifty-one".