87216921 has 27 divisors (see below), whose sum is σ = 138964917. Its totient is φ = 52671960.

The previous prime is 87216911. The next prime is 87216923. The reversal of 87216921 is 12961278.

The square root of 87216921 is 9339.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 87216921 - 2²³ = 78828313 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (87216923) 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 26 ways as a sum of consecutive naturals, for example, 308046 + ... + 308328.

Almost surely, 2^87216921 is an apocalyptic number.

87216921 is the 9339-th square number.

87216921 is the 4670-th centered octagonal number.

It is an amenable number.

87216921 is a deficient number, since it is larger than the sum of its proper divisors (51747996).

87216921 is a wasteful number, since it uses less digits than its factorization.

87216921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594 (or 297 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The cubic root of 87216921 is about 443.4727275061.

Multiplying 87216921 by its sum of digits (36), we get a square (3139809156 = 56034²).

The spelling of 87216921 in words is "eighty-seven million, two hundred sixteen thousand, nine hundred twenty-one".