1213781 has 2 divisors, whose sum is σ = 1213782. Its totient is φ = 1213780.

The previous prime is 1213763. The next prime is 1213801. The reversal of 1213781 is 1873121.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1060900 + 152881 = 1030^2 + 391^2 .

It is an emirp because it is prime and its reverse (1873121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1213781 - 2¹⁸ = 951637 is a prime.

It is a super-2 number, since 2×1213781² = 2946528631922, 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 (1213721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 606890 + 606891.

It is an arithmetic number, because the mean of its divisors is an integer number (606891).

2^1213781 is an apocalyptic number.

It is an amenable number.

1213781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1213781 is an equidigital number, since it uses as much as digits as its factorization.

1213781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 336, while the sum is 23.

The square root of 1213781 is about 1101.7172958613. The cubic root of 1213781 is about 106.6711011611.

The spelling of 1213781 in words is "one million, two hundred thirteen thousand, seven hundred eighty-one".