1681987 has 4 divisors (see below), whose sum is σ = 1684800. Its totient is φ = 1679176.

The previous prime is 1681973. The next prime is 1681991. The reversal of 1681987 is 7891861.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1681987 - 2¹¹ = 1679939 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

1681987 is a lucky number.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (1681907) 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, 112 + ... + 1837.

It is an arithmetic number, because the mean of its divisors is an integer number (421200).

2^1681987 is an apocalyptic number.

1681987 is a deficient number, since it is larger than the sum of its proper divisors (2813).

1681987 is an equidigital number, since it uses as much as digits as its factorization.

1681987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2812.

The product of its digits is 24192, while the sum is 40.

The square root of 1681987 is about 1296.9144150637. The cubic root of 1681987 is about 118.9252879430.

The spelling of 1681987 in words is "one million, six hundred eighty-one thousand, nine hundred eighty-seven".