87916921 has 8 divisors (see below), whose sum is σ = 91775624. Its totient is φ = 84136320.

The previous prime is 87916919. The next prime is 87916937. The reversal of 87916921 is 12961978.

It can be written as a sum of positive squares in 4 ways, for example, as 32205625 + 55711296 = 5675^2 + 7464^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 87916921 - 2¹ = 87916919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (87916981) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17220 + ... + 21733.

It is an arithmetic number, because the mean of its divisors is an integer number (11471953).

Almost surely, 2^87916921 is an apocalyptic number.

It is an amenable number.

87916921 is a deficient number, since it is larger than the sum of its proper divisors (3858703).

87916921 is a wasteful number, since it uses less digits than its factorization.

87916921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39051.

The product of its digits is 54432, while the sum is 43.

The square root of 87916921 is about 9376.4023484490. The cubic root of 87916921 is about 444.6559997676.

The spelling of 87916921 in words is "eighty-seven million, nine hundred sixteen thousand, nine hundred twenty-one".