2181556 has 12 divisors (see below), whose sum is σ = 4111492. Its totient is φ = 1006848.

The previous prime is 2181551. The next prime is 2181577. The reversal of 2181556 is 6551812.

It can be written as a sum of positive squares in 2 ways, for example, as 532900 + 1648656 = 730^2 + 1284^2 .

It is a super-2 number, since 2×2181556² = 9518373162272, which contains 22 as substring.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181551) 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, 20925 + ... + 21028.

2^2181556 is an apocalyptic number.

2181556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

2181556 is a deficient number, since it is larger than the sum of its proper divisors (1929936).

2181556 is a wasteful number, since it uses less digits than its factorization.

2181556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41970 (or 41968 counting only the distinct ones).

The product of its digits is 2400, while the sum is 28.

The square root of 2181556 is about 1477.0091401207. The cubic root of 2181556 is about 129.6946680414.

The spelling of 2181556 in words is "two million, one hundred eighty-one thousand, five hundred fifty-six".