821987 has 4 divisors (see below), whose sum is σ = 826440. Its totient is φ = 817536.

The previous prime is 821971. The next prime is 821993. The reversal of 821987 is 789128.

It is a happy number.

821987 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 821987 - 2⁴ = 821971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (827987) 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, 1937 + ... + 2322.

It is an arithmetic number, because the mean of its divisors is an integer number (206610).

2⁸²¹⁹⁸⁷ is an apocalyptic number.

821987 is a deficient number, since it is larger than the sum of its proper divisors (4453).

821987 is a wasteful number, since it uses less digits than its factorization.

821987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4452.

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

The square root of 821987 is about 906.6349871916. The cubic root of 821987 is about 93.6745573801.

The spelling of 821987 in words is "eight hundred twenty-one thousand, nine hundred eighty-seven".