216778121 has 4 divisors (see below), whose sum is σ = 247746432. Its totient is φ = 185809812.

The previous prime is 216778117. The next prime is 216778127. The reversal of 216778121 is 121877612.

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 216778121 - 2² = 216778117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216778127) 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, 15484145 + ... + 15484158.

It is an arithmetic number, because the mean of its divisors is an integer number (61936608).

Almost surely, 2^216778121 is an apocalyptic number.

It is an amenable number.

216778121 is a deficient number, since it is larger than the sum of its proper divisors (30968311).

216778121 is an equidigital number, since it uses as much as digits as its factorization.

216778121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30968310.

The product of its digits is 9408, while the sum is 35.

The square root of 216778121 is about 14723.3868725915. The cubic root of 216778121 is about 600.7196189766.

The spelling of 216778121 in words is "two hundred sixteen million, seven hundred seventy-eight thousand, one hundred twenty-one".