216556081 has 24 divisors (see below), whose sum is σ = 264894336. Its totient is φ = 173383680.

The previous prime is 216556069. The next prime is 216556097. The reversal of 216556081 is 180655612.

216556081 = 231² + 232² + ... + 871².

It is a happy number.

It is not a de Polignac number, because 216556081 - 2⁷ = 216555953 is a prime.

It is a super-2 number, since 2×216556081² = 93793072436157122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (216556031) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 337521 + ... + 338161.

It is an arithmetic number, because the mean of its divisors is an integer number (11037264).

Almost surely, 2^216556081 is an apocalyptic number.

It is an amenable number.

216556081 is a deficient number, since it is larger than the sum of its proper divisors (48338255).

216556081 is a wasteful number, since it uses less digits than its factorization.

216556081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 849 (or 832 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 216556081 is about 14715.8445561239. The cubic root of 216556081 is about 600.5144485932.

The spelling of 216556081 in words is "two hundred sixteen million, five hundred fifty-six thousand, eighty-one".