865087921 has 4 divisors (see below), whose sum is σ = 874808100. Its totient is φ = 855367744.

The previous prime is 865087919. The next prime is 865087933. The reversal of 865087921 is 129780568.

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

It can be written as a sum of positive squares in 2 ways, for example, as 472453696 + 392634225 = 21736^2 + 19815^2 .

It is a cyclic number.

It is not a de Polignac number, because 865087921 - 2¹ = 865087919 is a prime.

It is a super-2 number, since 2×865087921² = 1496754222120204482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (865087901) 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 3 ways as a sum of consecutive naturals, for example, 4859956 + ... + 4860133.

It is an arithmetic number, because the mean of its divisors is an integer number (218702025).

Almost surely, 2^865087921 is an apocalyptic number.

It is an amenable number.

865087921 is a deficient number, since it is larger than the sum of its proper divisors (9720179).

865087921 is an equidigital number, since it uses as much as digits as its factorization.

865087921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9720178.

The product of its (nonzero) digits is 241920, while the sum is 46.

The square root of 865087921 is about 29412.3770035677. The cubic root of 865087921 is about 952.8402243752.

The spelling of 865087921 in words is "eight hundred sixty-five million, eighty-seven thousand, nine hundred twenty-one".