216731381 has 2 divisors, whose sum is σ = 216731382. Its totient is φ = 216731380.

The previous prime is 216731327. The next prime is 216731387. The reversal of 216731381 is 183137612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 197852356 + 18879025 = 14066^2 + 4345^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216731381 is a prime.

It is a super-2 number, since 2×216731381² = 93944983020334322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216731387) 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 as a sum of consecutive naturals, namely, 108365690 + 108365691.

It is an arithmetic number, because the mean of its divisors is an integer number (108365691).

Almost surely, 2^216731381 is an apocalyptic number.

It is an amenable number.

216731381 is a deficient number, since it is larger than the sum of its proper divisors (1).

216731381 is an equidigital number, since it uses as much as digits as its factorization.

216731381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 32.

The square root of 216731381 is about 14721.7995163635. The cubic root of 216731381 is about 600.6764417207.

Adding to 216731381 its reverse (183137612), we get a palindrome (399868993).

The spelling of 216731381 in words is "two hundred sixteen million, seven hundred thirty-one thousand, three hundred eighty-one".