1981664 has 12 divisors (see below), whose sum is σ = 3901464. Its totient is φ = 990816.

The previous prime is 1981663. The next prime is 1981667. The reversal of 1981664 is 4661891.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30932 + ... + 30995.

It is an arithmetic number, because the mean of its divisors is an integer number (325122).

2^1981664 is an apocalyptic number.

It is an amenable number.

1981664 is a deficient number, since it is larger than the sum of its proper divisors (1919800).

1981664 is an equidigital number, since it uses as much as digits as its factorization.

1981664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61937 (or 61929 counting only the distinct ones).

The product of its digits is 10368, while the sum is 35.

The square root of 1981664 is about 1407.7158804247. The cubic root of 1981664 is about 125.6058904292.

The spelling of 1981664 in words is "one million, nine hundred eighty-one thousand, six hundred sixty-four".