2187721821 has 8 divisors (see below), whose sum is σ = 2917179360. Its totient is φ = 1458372752.

The previous prime is 2187721813. The next prime is 2187721849. The reversal of 2187721821 is 1281277812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2187721821 - 2³ = 2187721813 is a prime.

It is a super-2 number, since 2×2187721821² = 9572253532159112082, 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 2187721821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2187721021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59191 + ... + 88763.

It is an arithmetic number, because the mean of its divisors is an integer number (364647420).

Almost surely, 2^2187721821 is an apocalyptic number.

It is an amenable number.

2187721821 is a deficient number, since it is larger than the sum of its proper divisors (729457539).

2187721821 is a wasteful number, since it uses less digits than its factorization.

2187721821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54235.

The product of its digits is 25088, while the sum is 39.

The square root of 2187721821 is about 46773.0886407986. The cubic root of 2187721821 is about 1298.1674022363.

The spelling of 2187721821 in words is "two billion, one hundred eighty-seven million, seven hundred twenty-one thousand, eight hundred twenty-one".