642718079809 has 27 divisors (see below), whose sum is σ = 705396482787. Its totient is φ = 585341427216.

The previous prime is 642718079753. The next prime is 642718079813. The reversal of 642718079809 is 908970817246.

The square root of 642718079809 is 801697.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 95076639025 + 547641440784 = 308345^2 + 740028^2 .

It is not a de Polignac number, because 642718079809 - 2⁷ = 642718079681 is a prime.

It is a super-4 number, since 4×642718079809⁴ (a number of 48 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642718079309) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 865030692 + ... + 865031434.

Almost surely, 2^642718079809 is an apocalyptic number.

642718079809 is the 801697-th square number.

642718079809 is the 400849-th centered octagonal number.

It is an amenable number.

642718079809 is a deficient number, since it is larger than the sum of its proper divisors (62678402978).

642718079809 is an frugal number, since it uses more digits than its factorization.

642718079809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1678 (or 839 counting only the distinct ones).

The product of its (nonzero) digits is 12192768, while the sum is 61.

The spelling of 642718079809 in words is "six hundred forty-two billion, seven hundred eighteen million, seventy-nine thousand, eight hundred nine".