216721556 has 12 divisors (see below), whose sum is σ = 379392468. Its totient is φ = 108323712.

The previous prime is 216721529. The next prime is 216721567. The reversal of 216721556 is 655127612.

216721556 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 97693456 + 119028100 = 9884^2 + 10910^2 .

It is a super-2 number, since 2×216721556² = 93936465670122272, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7100 + ... + 21996.

It is an arithmetic number, because the mean of its divisors is an integer number (31616039).

Almost surely, 2^216721556 is an apocalyptic number.

It is an amenable number.

216721556 is a deficient number, since it is larger than the sum of its proper divisors (162670912).

216721556 is a wasteful number, since it uses less digits than its factorization.

216721556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18538 (or 18536 counting only the distinct ones).

The product of its digits is 25200, while the sum is 35.

The square root of 216721556 is about 14721.4658237555. The cubic root of 216721556 is about 600.6673648391.

The spelling of 216721556 in words is "two hundred sixteen million, seven hundred twenty-one thousand, five hundred fifty-six".