216821693 has 4 divisors (see below), whose sum is σ = 236532768. Its totient is φ = 197110620.

The previous prime is 216821687. The next prime is 216821729. The reversal of 216821693 is 396128612.

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 216821693 - 2⁴ = 216821677 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216821623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9855521 + ... + 9855542.

It is an arithmetic number, because the mean of its divisors is an integer number (59133192).

Almost surely, 2^216821693 is an apocalyptic number.

It is an amenable number.

216821693 is a deficient number, since it is larger than the sum of its proper divisors (19711075).

216821693 is a wasteful number, since it uses less digits than its factorization.

216821693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19711074.

The product of its digits is 31104, while the sum is 38.

The square root of 216821693 is about 14724.8664849635. The cubic root of 216821693 is about 600.7598641231.

The spelling of 216821693 in words is "two hundred sixteen million, eight hundred twenty-one thousand, six hundred ninety-three".