864821987 has 4 divisors (see below), whose sum is σ = 866002560. Its totient is φ = 863641416.

The previous prime is 864821981. The next prime is 864822017. The reversal of 864821987 is 789128468.

It is a happy number.

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 864821987 - 2¹⁴ = 864805603 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (864821981) 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, 589187 + ... + 590652.

It is an arithmetic number, because the mean of its divisors is an integer number (216500640).

Almost surely, 2^864821987 is an apocalyptic number.

864821987 is a deficient number, since it is larger than the sum of its proper divisors (1180573).

864821987 is a wasteful number, since it uses less digits than its factorization.

864821987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1180572.

The product of its digits is 1548288, while the sum is 53.

The square root of 864821987 is about 29407.8558721985. The cubic root of 864821987 is about 952.7425778142.

The spelling of 864821987 in words is "eight hundred sixty-four million, eight hundred twenty-one thousand, nine hundred eighty-seven".