1987917 has 4 divisors (see below), whose sum is σ = 2650560. Its totient is φ = 1325276.

The previous prime is 1987901. The next prime is 1987919. The reversal of 1987917 is 7197891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7197891 = 3 ⋅2399297.

It is a cyclic number.

It is not a de Polignac number, because 1987917 - 2⁴ = 1987901 is a prime.

It is a D-number.

1987917 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1987919) 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, 331317 + ... + 331322.

It is an arithmetic number, because the mean of its divisors is an integer number (662640).

2^1987917 is an apocalyptic number.

It is an amenable number.

1987917 is a deficient number, since it is larger than the sum of its proper divisors (662643).

1987917 is an equidigital number, since it uses as much as digits as its factorization.

1987917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 662642.

The product of its digits is 31752, while the sum is 42.

The square root of 1987917 is about 1409.9351048896. The cubic root of 1987917 is about 125.7378652027.

The spelling of 1987917 in words is "one million, nine hundred eighty-seven thousand, nine hundred seventeen".