781689989 has 2 divisors, whose sum is σ = 781689990. Its totient is φ = 781689988.

The previous prime is 781689977. The next prime is 781690003. The reversal of 781689989 is 989986187.

781689989 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 765352225 + 16337764 = 27665^2 + 4042^2 .

It is a cyclic number.

It is not a de Polignac number, because 781689989 - 2⁴ = 781689973 is a prime.

It is a super-2 number, since 2×781689989² = 1222078477805640242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781689919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390844994 + 390844995.

It is an arithmetic number, because the mean of its divisors is an integer number (390844995).

Almost surely, 2^781689989 is an apocalyptic number.

It is an amenable number.

781689989 is a deficient number, since it is larger than the sum of its proper divisors (1).

781689989 is an equidigital number, since it uses as much as digits as its factorization.

781689989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15676416, while the sum is 65.

The square root of 781689989 is about 27958.7193733905. The cubic root of 781689989 is about 921.1807417678.

The spelling of 781689989 in words is "seven hundred eighty-one million, six hundred eighty-nine thousand, nine hundred eighty-nine".