87912721 has 4 divisors (see below), whose sum is σ = 94675252. Its totient is φ = 81150192.

The previous prime is 87912709. The next prime is 87912731. The reversal of 87912721 is 12721978.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12721978 = 2 ⋅6360989.

It can be written as a sum of positive squares in 2 ways, for example, as 8346321 + 79566400 = 2889^2 + 8920^2 .

It is a cyclic number.

It is not a de Polignac number, because 87912721 - 2¹³ = 87904529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (87912731) 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, 3381246 + ... + 3381271.

It is an arithmetic number, because the mean of its divisors is an integer number (23668813).

Almost surely, 2^87912721 is an apocalyptic number.

It is an amenable number.

87912721 is a deficient number, since it is larger than the sum of its proper divisors (6762531).

87912721 is a wasteful number, since it uses less digits than its factorization.

87912721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6762530.

The product of its digits is 14112, while the sum is 37.

The square root of 87912721 is about 9376.1783792759. The cubic root of 87912721 is about 444.6489188973.

The spelling of 87912721 in words is "eighty-seven million, nine hundred twelve thousand, seven hundred twenty-one".