821321387 has 4 divisors (see below), whose sum is σ = 822415776. Its totient is φ = 820227000.

The previous prime is 821321377. The next prime is 821321419. The reversal of 821321387 is 783123128.

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 821321387 - 2¹² = 821317291 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821321377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 546068 + ... + 547569.

It is an arithmetic number, because the mean of its divisors is an integer number (205603944).

Almost surely, 2^821321387 is an apocalyptic number.

821321387 is a deficient number, since it is larger than the sum of its proper divisors (1094389).

821321387 is a wasteful number, since it uses less digits than its factorization.

821321387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1094388.

The product of its digits is 16128, while the sum is 35.

The square root of 821321387 is about 28658.7052568674. The cubic root of 821321387 is about 936.4926588498.

The spelling of 821321387 in words is "eight hundred twenty-one million, three hundred twenty-one thousand, three hundred eighty-seven".