1218631 has 2 divisors, whose sum is σ = 1218632. Its totient is φ = 1218630.

The previous prime is 1218617. The next prime is 1218649. The reversal of 1218631 is 1368121.

It is a weak prime.

It is an emirp because it is prime and its reverse (1368121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1218631 - 2¹¹ = 1216583 is a prime.

It is a super-2 number, since 2×1218631² = 2970123028322, which contains 22 as substring.

It is equal to p₉₄₂₅₂ and since 1218631 and 94252 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 13.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1218601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 609315 + 609316.

It is an arithmetic number, because the mean of its divisors is an integer number (609316).

2^1218631 is an apocalyptic number.

1218631 is a deficient number, since it is larger than the sum of its proper divisors (1).

1218631 is an equidigital number, since it uses as much as digits as its factorization.

1218631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 288, while the sum is 22.

The square root of 1218631 is about 1103.9162105885. The cubic root of 1218631 is about 106.8129903728.

It can be divided in two parts, 1218 and 631, that added together give a square (1849 = 43²).

The spelling of 1218631 in words is "one million, two hundred eighteen thousand, six hundred thirty-one".