1987821 has 40 divisors (see below), whose sum is σ = 3415104. Its totient is φ = 1140480.

The previous prime is 1987819. The next prime is 1987829. The reversal of 1987821 is 1287891.

It is not a de Polignac number, because 1987821 - 2¹ = 1987819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1987829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 20445 + ... + 20541.

2^1987821 is an apocalyptic number.

1987821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1987821 is a deficient number, since it is larger than the sum of its proper divisors (1427283).

1987821 is a wasteful number, since it uses less digits than its factorization.

1987821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143 (or 134 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 1987821 is about 1409.9010603585. The cubic root of 1987821 is about 125.7358411361.

The spelling of 1987821 in words is "one million, nine hundred eighty-seven thousand, eight hundred twenty-one".