2175868721645 has 18 divisors (see below), whose sum is σ = 2620564457406. Its totient is φ = 1734369994240.

The previous prime is 2175868721641. The next prime is 2175868721647. The reversal of 2175868721645 is 5461278685712.

It can be written as a sum of positive squares in 9 ways, for example, as 1783928867044 + 391939854601 = 1335638^2 + 626051^2 .

It is not a de Polignac number, because 2175868721645 - 2² = 2175868721641 is a prime.

It is a super-3 number, since 3×2175868721645³ (a number of 38 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2175868721641) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1045587005 + ... + 1045589085.

Almost surely, 2^{2175868721645} is an apocalyptic number.

It is an amenable number.

2175868721645 is a deficient number, since it is larger than the sum of its proper divisors (444695735761).

2175868721645 is an frugal number, since it uses more digits than its factorization.

2175868721645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4801 (or 2403 counting only the distinct ones).

The product of its digits is 45158400, while the sum is 62.

The spelling of 2175868721645 in words is "two trillion, one hundred seventy-five billion, eight hundred sixty-eight million, seven hundred twenty-one thousand, six hundred forty-five".