2161561725 has 54 divisors (see below), whose sum is σ = 3956633850. Its totient is φ = 1128045120.

The previous prime is 2161561723. The next prime is 2161561741. The reversal of 2161561725 is 5271651612.

2161561725 is a `hidden beast` number, since 2 + 1 + 6 + 15 + 617 + 25 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 9622404 + 2151939321 = 3102^2 + 46389^2 .

It is not a de Polignac number, because 2161561725 - 2¹ = 2161561723 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2161561725.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2161561723) by changing a digit.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 494851 + ... + 499199.

Almost surely, 2^2161561725 is an apocalyptic number.

2161561725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

2161561725 is a deficient number, since it is larger than the sum of its proper divisors (1795072125).

2161561725 is a wasteful number, since it uses less digits than its factorization.

2161561725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4459 (or 4404 counting only the distinct ones).

The product of its digits is 25200, while the sum is 36.

The square root of 2161561725 is about 46492.5986045091. The cubic root of 2161561725 is about 1292.9722791989.

The spelling of 2161561725 in words is "two billion, one hundred sixty-one million, five hundred sixty-one thousand, seven hundred twenty-five".