2180978721 has 6 divisors (see below), whose sum is σ = 3150302610. Its totient is φ = 1453985808.

The previous prime is 2180978713. The next prime is 2180978729. The reversal of 2180978721 is 1278790812.

It is an interprime number because it is at equal distance from previous prime (2180978713) and next prime (2180978729).

It can be written as a sum of positive squares in only one way, i.e., 1908728721 + 272250000 = 43689^2 + 16500^2 .

It is not a de Polignac number, because 2180978721 - 2³ = 2180978713 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2180978729) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 121165476 + ... + 121165493.

It is an arithmetic number, because the mean of its divisors is an integer number (525050435).

Almost surely, 2^2180978721 is an apocalyptic number.

It is an amenable number.

2180978721 is a deficient number, since it is larger than the sum of its proper divisors (969323889).

2180978721 is a wasteful number, since it uses less digits than its factorization.

2180978721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242330975 (or 242330972 counting only the distinct ones).

The product of its (nonzero) digits is 112896, while the sum is 45.

The square root of 2180978721 is about 46700.9498939797. The cubic root of 2180978721 is about 1296.8322718402.

The spelling of 2180978721 in words is "two billion, one hundred eighty million, nine hundred seventy-eight thousand, seven hundred twenty-one".