216907381 has 2 divisors, whose sum is σ = 216907382. Its totient is φ = 216907380.

The previous prime is 216907373. The next prime is 216907421. The reversal of 216907381 is 183709612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168117156 + 48790225 = 12966^2 + 6985^2 .

It is a cyclic number.

It is not a de Polignac number, because 216907381 - 2³ = 216907373 is a prime.

It is a super-2 number, since 2×216907381² = 94097623864558322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 216907381.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216904381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108453690 + 108453691.

It is an arithmetic number, because the mean of its divisors is an integer number (108453691).

Almost surely, 2^216907381 is an apocalyptic number.

It is an amenable number.

216907381 is a deficient number, since it is larger than the sum of its proper divisors (1).

216907381 is an equidigital number, since it uses as much as digits as its factorization.

216907381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 37.

The square root of 216907381 is about 14727.7758334380. The cubic root of 216907381 is about 600.8389938613.

The spelling of 216907381 in words is "two hundred sixteen million, nine hundred seven thousand, three hundred eighty-one".