2165878521 has 15 divisors (see below), whose sum is σ = 3236073973. Its totient is φ = 1443639780.

The previous prime is 2165878511. The next prime is 2165878577. The reversal of 2165878521 is 1258785612.

The square root of 2165878521 is 46539.

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

2165878521 is a `hidden beast` number, since 2 + 1 + 6 + 58 + 78 + 521 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-2165878521 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2165878511) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 416266 + ... + 421436.

Almost surely, 2^2165878521 is an apocalyptic number.

2165878521 is the 46539-th square number.

2165878521 is the 23270-th centered octagonal number.

It is an amenable number.

2165878521 is a deficient number, since it is larger than the sum of its proper divisors (1070195452).

2165878521 is an frugal number, since it uses more digits than its factorization.

2165878521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10354 (or 5174 counting only the distinct ones).

The product of its digits is 268800, while the sum is 45.

The cubic root of 2165878521 is about 1293.8324267584.

The spelling of 2165878521 in words is "two billion, one hundred sixty-five million, eight hundred seventy-eight thousand, five hundred twenty-one".