1981987 has 8 divisors (see below), whose sum is σ = 2304000. Its totient is φ = 1669704.

The previous prime is 1981963. The next prime is 1981997. The reversal of 1981987 is 7891891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981987 is a prime.

It is a Duffinian number.

1981987 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1981997) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1987 + ... + 2812.

It is an arithmetic number, because the mean of its divisors is an integer number (288000).

2^1981987 is an apocalyptic number.

1981987 is a deficient number, since it is larger than the sum of its proper divisors (322013).

1981987 is an equidigital number, since it uses as much as digits as its factorization.

1981987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4865.

The product of its digits is 36288, while the sum is 43.

The square root of 1981987 is about 1407.8306006051. The cubic root of 1981987 is about 125.6127144079.

The spelling of 1981987 in words is "one million, nine hundred eighty-one thousand, nine hundred eighty-seven".