1217779813 has 2 divisors, whose sum is σ = 1217779814. Its totient is φ = 1217779812.

The previous prime is 1217779777. The next prime is 1217779841. The reversal of 1217779813 is 3189777121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 883694529 + 334085284 = 29727^2 + 18278^2 .

It is a cyclic number.

It is not a de Polignac number, because 1217779813 - 2⁹ = 1217779301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1217729813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608889906 + 608889907.

It is an arithmetic number, because the mean of its divisors is an integer number (608889907).

Almost surely, 2^1217779813 is an apocalyptic number.

It is an amenable number.

1217779813 is a deficient number, since it is larger than the sum of its proper divisors (1).

1217779813 is an equidigital number, since it uses as much as digits as its factorization.

1217779813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 148176, while the sum is 46.

The square root of 1217779813 is about 34896.7020361524. The cubic root of 1217779813 is about 1067.8811573752.

The spelling of 1217779813 in words is "one billion, two hundred seventeen million, seven hundred seventy-nine thousand, eight hundred thirteen".