2185981 has 4 divisors (see below), whose sum is σ = 2498272. Its totient is φ = 1873692.

The previous prime is 2185973. The next prime is 2185987. The reversal of 2185981 is 1895812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2185981 - 2³ = 2185973 is a prime.

It is a super-2 number, since 2×2185981² = 9557025864722, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2185987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156135 + ... + 156148.

It is an arithmetic number, because the mean of its divisors is an integer number (624568).

2^2185981 is an apocalyptic number.

It is an amenable number.

2185981 is a deficient number, since it is larger than the sum of its proper divisors (312291).

2185981 is an equidigital number, since it uses as much as digits as its factorization.

2185981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312290.

The product of its digits is 5760, while the sum is 34.

The square root of 2185981 is about 1478.5063408724. The cubic root of 2185981 is about 129.7822983561.

It can be divided in two parts, 2185 and 981, that multiplied together give a triangular number (2143485 = T₂₀₇₀).

The spelling of 2185981 in words is "two million, one hundred eighty-five thousand, nine hundred eighty-one".