645873643 has 4 divisors (see below), whose sum is σ = 647790520. Its totient is φ = 643956768.

The previous prime is 645873601. The next prime is 645873653. The reversal of 645873643 is 346378546.

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 645873643 - 2¹⁷ = 645742571 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 645873593 and 645873602.

It is not an unprimeable number, because it can be changed into a prime (645873653) 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, 957933 + ... + 958606.

It is an arithmetic number, because the mean of its divisors is an integer number (161947630).

Almost surely, 2^645873643 is an apocalyptic number.

645873643 is a deficient number, since it is larger than the sum of its proper divisors (1916877).

645873643 is a wasteful number, since it uses less digits than its factorization.

645873643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1916876.

The product of its digits is 1451520, while the sum is 46.

The square root of 645873643 is about 25414.0442078784. The cubic root of 645873643 is about 864.4021810699.

The spelling of 645873643 in words is "six hundred forty-five million, eight hundred seventy-three thousand, six hundred forty-three".