2187721820 has 36 divisors (see below), whose sum is σ = 4802672280. Its totient is φ = 837037344.

The previous prime is 2187721813. The next prime is 2187721849. The reversal of 2187721820 is 281277812.

2187721820 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 2×2187721820² = 9572253523408224800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 92810 + ... + 113969.

Almost surely, 2^2187721820 is an apocalyptic number.

2187721820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2187721820 is an abundant number, since it is smaller than the sum of its proper divisors (2614950460).

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

2187721820 is a wasteful number, since it uses less digits than its factorization.

2187721820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206834 (or 206809 counting only the distinct ones).

The product of its (nonzero) digits is 25088, while the sum is 38.

The square root of 2187721820 is about 46773.0886301087. The cubic root of 2187721820 is about 1298.1674020385.

The spelling of 2187721820 in words is "two billion, one hundred eighty-seven million, seven hundred twenty-one thousand, eight hundred twenty".