87147821 has 4 divisors (see below), whose sum is σ = 88127100. Its totient is φ = 86168544.

The previous prime is 87147817. The next prime is 87147829. The reversal of 87147821 is 12874178.

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 44702596 + 42445225 = 6686^2 + 6515^2 .

It is a cyclic number.

It is not a de Polignac number, because 87147821 - 2² = 87147817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (87147829) 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, 489506 + ... + 489683.

It is an arithmetic number, because the mean of its divisors is an integer number (22031775).

Almost surely, 2^87147821 is an apocalyptic number.

It is an amenable number.

87147821 is a deficient number, since it is larger than the sum of its proper divisors (979279).

87147821 is an equidigital number, since it uses as much as digits as its factorization.

87147821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 979278.

The product of its digits is 25088, while the sum is 38.

The square root of 87147821 is about 9335.2997273789. The cubic root of 87147821 is about 443.3555787482.

The spelling of 87147821 in words is "eighty-seven million, one hundred forty-seven thousand, eight hundred twenty-one".