1981684 has 6 divisors (see below), whose sum is σ = 3467954. Its totient is φ = 990840.

The previous prime is 1981669. The next prime is 1981687. The reversal of 1981684 is 4861891.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1904400 + 77284 = 1380^2 + 278^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981687) 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 as a sum of consecutive naturals, namely, 247707 + ... + 247714.

2^1981684 is an apocalyptic number.

It is an amenable number.

1981684 is a deficient number, since it is larger than the sum of its proper divisors (1486270).

1981684 is a wasteful number, since it uses less digits than its factorization.

1981684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 495425 (or 495423 counting only the distinct ones).

The product of its digits is 13824, while the sum is 37.

The square root of 1981684 is about 1407.7229841130. The cubic root of 1981684 is about 125.6063129882.

It can be divided in two parts, 19816 and 84, that added together give a triangular number (19900 = T₁₉₉).

The spelling of 1981684 in words is "one million, nine hundred eighty-one thousand, six hundred eighty-four".