645857551 has 2 divisors, whose sum is σ = 645857552. Its totient is φ = 645857550.

The previous prime is 645857507. The next prime is 645857561. The reversal of 645857551 is 155758546.

645857551 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645857551 - 2⁷ = 645857423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645857561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322928775 + 322928776.

It is an arithmetic number, because the mean of its divisors is an integer number (322928776).

Almost surely, 2^645857551 is an apocalyptic number.

645857551 is a deficient number, since it is larger than the sum of its proper divisors (1).

645857551 is an equidigital number, since it uses as much as digits as its factorization.

645857551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 840000, while the sum is 46.

The square root of 645857551 is about 25413.7276093060. The cubic root of 645857551 is about 864.3950021242.

It can be divided in two parts, 6458 and 57551, that added together give a square (64009 = 253²).

The spelling of 645857551 in words is "six hundred forty-five million, eight hundred fifty-seven thousand, five hundred fifty-one".