216661556 has 12 divisors (see below), whose sum is σ = 381484992. Its totient is φ = 107665848.

The previous prime is 216661553. The next prime is 216661661. The reversal of 216661556 is 655166612.

It is a super-2 number, since 2×216661556² = 93884459696682272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216661553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165500 + ... + 166803.

It is an arithmetic number, because the mean of its divisors is an integer number (31790416).

Almost surely, 2^216661556 is an apocalyptic number.

It is an amenable number.

216661556 is a deficient number, since it is larger than the sum of its proper divisors (164823436).

216661556 is a wasteful number, since it uses less digits than its factorization.

216661556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332470 (or 332468 counting only the distinct ones).

The product of its digits is 64800, while the sum is 38.

The square root of 216661556 is about 14719.4278421411. The cubic root of 216661556 is about 600.6119275475.

The spelling of 216661556 in words is "two hundred sixteen million, six hundred sixty-one thousand, five hundred fifty-six".