216331661 has 12 divisors (see below), whose sum is σ = 267718752. Its totient is φ = 171162576.

The previous prime is 216331651. The next prime is 216331669. The reversal of 216331661 is 166133612.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-216331661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216331669) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 90251 + ... + 92616.

It is an arithmetic number, because the mean of its divisors is an integer number (22309896).

Almost surely, 2^216331661 is an apocalyptic number.

It is an amenable number.

216331661 is a deficient number, since it is larger than the sum of its proper divisors (51387091).

216331661 is a wasteful number, since it uses less digits than its factorization.

216331661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182900 (or 182887 counting only the distinct ones).

The product of its digits is 3888, while the sum is 29.

The square root of 216331661 is about 14708.2174650771. The cubic root of 216331661 is about 600.3069364751.

The spelling of 216331661 in words is "two hundred sixteen million, three hundred thirty-one thousand, six hundred sixty-one".