645704257551 has 4 divisors (see below), whose sum is σ = 860939010072. Its totient is φ = 430469505032.

The previous prime is 645704257543. The next prime is 645704257553. The reversal of 645704257551 is 155752407546.

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 645704257551 - 2³ = 645704257543 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 645704257494 and 645704257503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645704257553) 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, 107617376256 + ... + 107617376261.

It is an arithmetic number, because the mean of its divisors is an integer number (215234752518).

Almost surely, 2^645704257551 is an apocalyptic number.

645704257551 is a deficient number, since it is larger than the sum of its proper divisors (215234752521).

645704257551 is a wasteful number, since it uses less digits than its factorization.

645704257551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215234752520.

The product of its (nonzero) digits is 5880000, while the sum is 51.

The spelling of 645704257551 in words is "six hundred forty-five billion, seven hundred four million, two hundred fifty-seven thousand, five hundred fifty-one".