221801816 has 24 divisors (see below), whose sum is σ = 418685580. Its totient is φ = 110155968.

The previous prime is 221801809. The next prime is 221801819. The reversal of 221801816 is 618108122.

221801816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221801819) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 708476 + ... + 708788.

Almost surely, 2^221801816 is an apocalyptic number.

It is an amenable number.

221801816 is a deficient number, since it is larger than the sum of its proper divisors (196883764).

221801816 is an equidigital number, since it uses as much as digits as its factorization.

221801816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 915 (or 598 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 29.

The square root of 221801816 is about 14893.0123212196. The cubic root of 221801816 is about 605.3246587517.

Adding to 221801816 its reverse (618108122), we get a palindrome (839909938).

The spelling of 221801816 in words is "two hundred twenty-one million, eight hundred one thousand, eight hundred sixteen".