87818821 has 4 divisors (see below), whose sum is σ = 92984652. Its totient is φ = 82652992.

The previous prime is 87818803. The next prime is 87818831. The reversal of 87818821 is 12881878.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12881878 = 2 ⋅6440939.

It can be written as a sum of positive squares in 2 ways, for example, as 36180225 + 51638596 = 6015^2 + 7186^2 .

It is a cyclic number.

It is not a de Polignac number, because 87818821 - 2⁵ = 87818789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (87818831) 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, 2582890 + ... + 2582923.

It is an arithmetic number, because the mean of its divisors is an integer number (23246163).

Almost surely, 2^87818821 is an apocalyptic number.

It is an amenable number.

87818821 is a deficient number, since it is larger than the sum of its proper divisors (5165831).

87818821 is a wasteful number, since it uses less digits than its factorization.

87818821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5165830.

The product of its digits is 57344, while the sum is 43.

The square root of 87818821 is about 9371.1696708575. The cubic root of 87818821 is about 444.4905519504.

The spelling of 87818821 in words is "eighty-seven million, eight hundred eighteen thousand, eight hundred twenty-one".