2181780 has 144 divisors (see below), whose sum is σ = 7547904. Its totient is φ = 506880.

The previous prime is 2181737. The next prime is 2181833. The reversal of 2181780 is 871812.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 70365 + ... + 70395.

It is an arithmetic number, because the mean of its divisors is an integer number (52416).

2^2181780 is an apocalyptic number.

2181780 is a gapful number since it is divisible by the number (20) 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 2181780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3773952).

2181780 is an abundant number, since it is smaller than the sum of its proper divisors (5366124).

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

2181780 is a wasteful number, since it uses less digits than its factorization.

2181780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86 (or 81 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 2181780 is about 1477.0849670889. The cubic root of 2181780 is about 129.6991068627.

The spelling of 2181780 in words is "two million, one hundred eighty-one thousand, seven hundred eighty".