642568749 has 4 divisors (see below), whose sum is σ = 856758336. Its totient is φ = 428379164.

The previous prime is 642568727. The next prime is 642568753. The reversal of 642568749 is 947865246.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 642568749 - 2⁷ = 642568621 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642568709) 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, 107094789 + ... + 107094794.

It is an arithmetic number, because the mean of its divisors is an integer number (214189584).

Almost surely, 2^642568749 is an apocalyptic number.

It is an amenable number.

642568749 is a deficient number, since it is larger than the sum of its proper divisors (214189587).

642568749 is a wasteful number, since it uses less digits than its factorization.

642568749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214189586.

The product of its digits is 2903040, while the sum is 51.

The square root of 642568749 is about 25348.9398003151. The cubic root of 642568749 is about 862.9252956518.

The spelling of 642568749 in words is "six hundred forty-two million, five hundred sixty-eight thousand, seven hundred forty-nine".