2187721878 has 64 divisors (see below), whose sum is σ = 4554178560. Its totient is φ = 700176672.

The previous prime is 2187721849. The next prime is 2187721897. The reversal of 2187721878 is 8781277812.

2187721878 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×2187721878² = 9572254030959693768, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 2187721878.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6304501 + ... + 6304847.

It is an arithmetic number, because the mean of its divisors is an integer number (71159040).

Almost surely, 2^2187721878 is an apocalyptic number.

2187721878 is an abundant number, since it is smaller than the sum of its proper divisors (2366456682).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

2187721878 is a wasteful number, since it uses less digits than its factorization.

2187721878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 761.

The product of its digits is 702464, while the sum is 51.

The square root of 2187721878 is about 46773.0892501233. The cubic root of 2187721878 is about 1298.1674135106.

The spelling of 2187721878 in words is "two billion, one hundred eighty-seven million, seven hundred twenty-one thousand, eight hundred seventy-eight".