2171988 has 144 divisors (see below), whose sum is σ = 7378560. Its totient is φ = 539136.

The previous prime is 2171977. The next prime is 2171989. The reversal of 2171988 is 8891712.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

Its product of digits (8064) is a multiple of the sum of its prime divisors (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2171989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 127756 + ... + 127772.

It is an arithmetic number, because the mean of its divisors is an integer number (51240).

2^2171988 is an apocalyptic number.

2171988 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2171988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3689280).

2171988 is an abundant number, since it is smaller than the sum of its proper divisors (5206572).

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

2171988 is a wasteful number, since it uses less digits than its factorization.

2171988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63 (or 42 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 2171988 is about 1473.7666029599. The cubic root of 2171988 is about 129.5047825984.

The spelling of 2171988 in words is "two million, one hundred seventy-one thousand, nine hundred eighty-eight".