645167551 has 4 divisors (see below), whose sum is σ = 737334352. Its totient is φ = 553000752.

The previous prime is 645167507. The next prime is 645167573. The reversal of 645167551 is 155761546.

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 645167551 - 2⁷ = 645167423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645167951) 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, 46083390 + ... + 46083403.

It is an arithmetic number, because the mean of its divisors is an integer number (184333588).

Almost surely, 2^645167551 is an apocalyptic number.

645167551 is a deficient number, since it is larger than the sum of its proper divisors (92166801).

645167551 is an equidigital number, since it uses as much as digits as its factorization.

645167551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92166800.

The product of its digits is 126000, while the sum is 40.

The square root of 645167551 is about 25400.1486412974. The cubic root of 645167551 is about 864.0870678253.

It can be divided in two parts, 64 and 5167551, that added together give a palindrome (5167615).

The spelling of 645167551 in words is "six hundred forty-five million, one hundred sixty-seven thousand, five hundred fifty-one".