987821 has 2 divisors, whose sum is σ = 987822. Its totient is φ = 987820.

The previous prime is 987809. The next prime is 987851. The reversal of 987821 is 128789.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 972196 + 15625 = 986^2 + 125^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-987821 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (987851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 493910 + 493911.

It is an arithmetic number, because the mean of its divisors is an integer number (493911).

2⁹⁸⁷⁸²¹ is an apocalyptic number.

It is an amenable number.

987821 is a deficient number, since it is larger than the sum of its proper divisors (1).

987821 is an equidigital number, since it uses as much as digits as its factorization.

987821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8064, while the sum is 35.

The square root of 987821 is about 993.8918452226. The cubic root of 987821 is about 99.5923740015.

The spelling of 987821 in words is "nine hundred eighty-seven thousand, eight hundred twenty-one".