216536821 has 4 divisors (see below), whose sum is σ = 216582444. Its totient is φ = 216491200.

The previous prime is 216536819. The next prime is 216536897. The reversal of 216536821 is 128635612.

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 39513796 + 177023025 = 6286^2 + 13305^2 .

It is a cyclic number.

It is not a de Polignac number, because 216536821 - 2¹ = 216536819 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 (216536921) 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, 14740 + ... + 25501.

It is an arithmetic number, because the mean of its divisors is an integer number (54145611).

Almost surely, 2^216536821 is an apocalyptic number.

It is an amenable number.

216536821 is a deficient number, since it is larger than the sum of its proper divisors (45623).

216536821 is an equidigital number, since it uses as much as digits as its factorization.

216536821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45622.

The product of its digits is 17280, while the sum is 34.

The square root of 216536821 is about 14715.1901448809. The cubic root of 216536821 is about 600.4966452738.

The spelling of 216536821 in words is "two hundred sixteen million, five hundred thirty-six thousand, eight hundred twenty-one".