2181551987 has 4 divisors (see below), whose sum is σ = 2181779376. Its totient is φ = 2181324600.

The previous prime is 2181551923. The next prime is 2181551989. The reversal of 2181551987 is 7891551812.

2181551987 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 2181551987 - 2⁶ = 2181551923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2181551989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 98639 + ... + 118712.

It is an arithmetic number, because the mean of its divisors is an integer number (545444844).

Almost surely, 2^2181551987 is an apocalyptic number.

2181551987 is a deficient number, since it is larger than the sum of its proper divisors (227389).

2181551987 is a wasteful number, since it uses less digits than its factorization.

2181551987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227388.

The product of its digits is 201600, while the sum is 47.

The square root of 2181551987 is about 46707.0871174814. The cubic root of 2181551987 is about 1296.9458851636.

The spelling of 2181551987 in words is "two billion, one hundred eighty-one million, five hundred fifty-one thousand, nine hundred eighty-seven".