216632781 has 12 divisors (see below), whose sum is σ = 314664480. Its totient is φ = 143613960.

The previous prime is 216632761. The next prime is 216632789. The reversal of 216632781 is 187236612.

216632781 is a `hidden beast` number, since 2 + 16 + 632 + 7 + 8 + 1 = 666.

It is not a de Polignac number, because 216632781 - 2¹⁰ = 216631757 is a prime.

It is a super-2 number, since 2×216632781² = 93859523607587922, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216632789) 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, 65625 + ... + 68846.

It is an arithmetic number, because the mean of its divisors is an integer number (26222040).

Almost surely, 2^216632781 is an apocalyptic number.

It is an amenable number.

216632781 is a deficient number, since it is larger than the sum of its proper divisors (98031699).

216632781 is a wasteful number, since it uses less digits than its factorization.

216632781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134656 (or 134653 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 216632781 is about 14718.4503600073. The cubic root of 216632781 is about 600.5853371151.

The spelling of 216632781 in words is "two hundred sixteen million, six hundred thirty-two thousand, seven hundred eighty-one".