1666987 has 4 divisors (see below), whose sum is σ = 1905136. Its totient is φ = 1428840.

The previous prime is 1666943. The next prime is 1666991. The reversal of 1666987 is 7896661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7896661 = 31 ⋅254731.

It is a de Polignac number, because none of the positive numbers 2^k-1666987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666387) 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, 119064 + ... + 119077.

It is an arithmetic number, because the mean of its divisors is an integer number (476284).

2^1666987 is an apocalyptic number.

1666987 is a deficient number, since it is larger than the sum of its proper divisors (238149).

1666987 is an equidigital number, since it uses as much as digits as its factorization.

1666987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238148.

The product of its digits is 108864, while the sum is 43.

The square root of 1666987 is about 1291.1185073416. The cubic root of 1666987 is about 118.5707056063.

The spelling of 1666987 in words is "one million, six hundred sixty-six thousand, nine hundred eighty-seven".