781456021813 has 2 divisors, whose sum is σ = 781456021814. Its totient is φ = 781456021812.

The previous prime is 781456021769. The next prime is 781456021837. The reversal of 781456021813 is 318120654187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 603879747409 + 177576274404 = 777097^2 + 421398^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-781456021813 is a prime.

It is a super-2 number, since 2×781456021813² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781456021883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390728010906 + 390728010907.

It is an arithmetic number, because the mean of its divisors is an integer number (390728010907).

Almost surely, 2^781456021813 is an apocalyptic number.

It is an amenable number.

781456021813 is a deficient number, since it is larger than the sum of its proper divisors (1).

781456021813 is an equidigital number, since it uses as much as digits as its factorization.

781456021813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 322560, while the sum is 46.

The spelling of 781456021813 in words is "seven hundred eighty-one billion, four hundred fifty-six million, twenty-one thousand, eight hundred thirteen".