1987391 has 6 divisors (see below), whose sum is σ = 2311920. Its totient is φ = 1703436.

The previous prime is 1987373. The next prime is 1987411. The reversal of 1987391 is 1937891.

It is not a de Polignac number, because 1987391 - 2¹⁴ = 1971007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1987091) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 20231 + ... + 20328.

It is an arithmetic number, because the mean of its divisors is an integer number (385320).

2^1987391 is an apocalyptic number.

1987391 is a deficient number, since it is larger than the sum of its proper divisors (324529).

1987391 is an equidigital number, since it uses as much as digits as its factorization.

1987391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40573 (or 40566 counting only the distinct ones).

The product of its digits is 13608, while the sum is 38.

The square root of 1987391 is about 1409.7485591410. The cubic root of 1987391 is about 125.7267742045.

The spelling of 1987391 in words is "one million, nine hundred eighty-seven thousand, three hundred ninety-one".