218400631 has 2 divisors, whose sum is σ = 218400632. Its totient is φ = 218400630.

The previous prime is 218400629. The next prime is 218400643. The reversal of 218400631 is 136004812.

218400631 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 218400631 - 2¹ = 218400629 is a prime.

It is a super-2 number, since 2×218400631² = 95397671242396322, which contains 22 as substring.

Together with 218400629, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 218400596 and 218400605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218400671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109200315 + 109200316.

It is an arithmetic number, because the mean of its divisors is an integer number (109200316).

Almost surely, 2^218400631 is an apocalyptic number.

218400631 is a deficient number, since it is larger than the sum of its proper divisors (1).

218400631 is an equidigital number, since it uses as much as digits as its factorization.

218400631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 218400631 is about 14778.3839102928. The cubic root of 218400631 is about 602.2146221721.

The spelling of 218400631 in words is "two hundred eighteen million, four hundred thousand, six hundred thirty-one".