645473251 has 4 divisors (see below), whose sum is σ = 662918512. Its totient is φ = 628027992.

The previous prime is 645473239. The next prime is 645473261. The reversal of 645473251 is 152374546.

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-645473251 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 17445223 = 645473251 / (6 + 4 + 5 + 4 + 7 + 3 + 2 + 5 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645473251.

It is not an unprimeable number, because it can be changed into a prime (645473201) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8722575 + ... + 8722648.

It is an arithmetic number, because the mean of its divisors is an integer number (165729628).

Almost surely, 2^645473251 is an apocalyptic number.

645473251 is a deficient number, since it is larger than the sum of its proper divisors (17445261).

645473251 is a wasteful number, since it uses less digits than its factorization.

645473251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17445260.

The product of its digits is 100800, while the sum is 37.

The square root of 645473251 is about 25406.1656099459. The cubic root of 645473251 is about 864.2235231829.

The spelling of 645473251 in words is "six hundred forty-five million, four hundred seventy-three thousand, two hundred fifty-one".