645254871 has 4 divisors (see below), whose sum is σ = 860339832. Its totient is φ = 430169912.

The previous prime is 645254851. The next prime is 645254879. The reversal of 645254871 is 178452546.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645254871 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645254879) 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, 107542476 + ... + 107542481.

It is an arithmetic number, because the mean of its divisors is an integer number (215084958).

Almost surely, 2^645254871 is an apocalyptic number.

645254871 is a deficient number, since it is larger than the sum of its proper divisors (215084961).

645254871 is a wasteful number, since it uses less digits than its factorization.

645254871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215084960.

The product of its digits is 268800, while the sum is 42.

The square root of 645254871 is about 25401.8674707195. The cubic root of 645254871 is about 864.1260492645.

It can be divided in two parts, 64525 and 4871, that added together give a palindrome (69396).

The spelling of 645254871 in words is "six hundred forty-five million, two hundred fifty-four thousand, eight hundred seventy-one".