216696821 has 4 divisors (see below), whose sum is σ = 236396544. Its totient is φ = 196997100.

The previous prime is 216696817. The next prime is 216696847. The reversal of 216696821 is 128696612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216696821 - 2² = 216696817 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 (216636821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9849845 + ... + 9849866.

It is an arithmetic number, because the mean of its divisors is an integer number (59099136).

Almost surely, 2^216696821 is an apocalyptic number.

It is an amenable number.

216696821 is a deficient number, since it is larger than the sum of its proper divisors (19699723).

216696821 is a wasteful number, since it uses less digits than its factorization.

216696821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19699722.

The product of its digits is 62208, while the sum is 41.

The square root of 216696821 is about 14720.6257000170. The cubic root of 216696821 is about 600.6445120554.

The spelling of 216696821 in words is "two hundred sixteen million, six hundred ninety-six thousand, eight hundred twenty-one".