216821256 has 16 divisors (see below), whose sum is σ = 542053200. Its totient is φ = 72273744.

The previous prime is 216821249. The next prime is 216821257. The reversal of 216821256 is 652128612.

It is a super-2 number, since 2×216821256² = 94022914106835072, which contains 22 as substring.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (216821257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4517086 + ... + 4517133.

It is an arithmetic number, because the mean of its divisors is an integer number (33878325).

Almost surely, 2^216821256 is an apocalyptic number.

It is an amenable number.

216821256 is an abundant number, since it is smaller than the sum of its proper divisors (325231944).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

216821256 is a wasteful number, since it uses less digits than its factorization.

216821256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9034228 (or 9034224 counting only the distinct ones).

The product of its digits is 11520, while the sum is 33.

The square root of 216821256 is about 14724.8516461118. The cubic root of 216821256 is about 600.7594605162.

Adding to 216821256 its reverse (652128612), we get a palindrome (868949868).

The spelling of 216821256 in words is "two hundred sixteen million, eight hundred twenty-one thousand, two hundred fifty-six".