781321 has 2 divisors, whose sum is σ = 781322. Its totient is φ = 781320.

The previous prime is 781309. The next prime is 781327. The reversal of 781321 is 123187.

781321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 741321 + 40000 = 861^2 + 200^2 .

It is a cyclic number.

It is not a de Polignac number, because 781321 - 2⁹ = 780809 is a prime.

It is a super-2 number, since 2×781321² = 1220925010082, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 781292 and 781301.

It is not a weakly prime, because it can be changed into another prime (781327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390660 + 390661.

It is an arithmetic number, because the mean of its divisors is an integer number (390661).

2⁷⁸¹³²¹ is an apocalyptic number.

It is an amenable number.

781321 is a deficient number, since it is larger than the sum of its proper divisors (1).

781321 is an equidigital number, since it uses as much as digits as its factorization.

781321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 336, while the sum is 22.

The square root of 781321 is about 883.9236392359. The cubic root of 781321 is about 92.1035774213.

The spelling of 781321 in words is "seven hundred eighty-one thousand, three hundred twenty-one".