643665280555 has 16 divisors (see below), whose sum is σ = 858514793184. Its totient is φ = 459287745280.

The previous prime is 643665280523. The next prime is 643665280591. The reversal of 643665280555 is 555082566346.

It is a happy number.

It is not a de Polignac number, because 643665280555 - 2⁵ = 643665280523 is a prime.

It is a super-2 number, since 2×643665280555² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643665280496 and 643665280505.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 110402794 + ... + 110408623.

It is an arithmetic number, because the mean of its divisors is an integer number (53657174574).

Almost surely, 2^643665280555 is an apocalyptic number.

643665280555 is a deficient number, since it is larger than the sum of its proper divisors (214849512629).

643665280555 is a wasteful number, since it uses less digits than its factorization.

643665280555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220811486.

The product of its (nonzero) digits is 25920000, while the sum is 55.

The spelling of 643665280555 in words is "six hundred forty-three billion, six hundred sixty-five million, two hundred eighty thousand, five hundred fifty-five".