216655939921 has 4 divisors (see below), whose sum is σ = 216660815344. Its totient is φ = 216651064500.

The previous prime is 216655939889. The next prime is 216655939931. The reversal of 216655939921 is 129939556612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216655939921 - 2⁵ = 216655939889 is a prime.

It is a super-2 number, since 2×216655939921² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216655939931) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2370435 + ... + 2460136.

It is an arithmetic number, because the mean of its divisors is an integer number (54165203836).

Almost surely, 2^216655939921 is an apocalyptic number.

It is an amenable number.

216655939921 is a deficient number, since it is larger than the sum of its proper divisors (4875423).

216655939921 is an equidigital number, since it uses as much as digits as its factorization.

216655939921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4875422.

The product of its digits is 7873200, while the sum is 58.

The spelling of 216655939921 in words is "two hundred sixteen billion, six hundred fifty-five million, nine hundred thirty-nine thousand, nine hundred twenty-one".