781320691 has 2 divisors, whose sum is σ = 781320692. Its totient is φ = 781320690.

The previous prime is 781320667. The next prime is 781320719. The reversal of 781320691 is 196023187.

It is a weak prime.

It is an emirp because it is prime and its reverse (196023187) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-781320691 is a prime.

It is a super-2 number, since 2×781320691² = 1220924044369434962, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 781320691.

It is not a weakly prime, because it can be changed into another prime (781326691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390660345 + 390660346.

It is an arithmetic number, because the mean of its divisors is an integer number (390660346).

Almost surely, 2^781320691 is an apocalyptic number.

781320691 is a deficient number, since it is larger than the sum of its proper divisors (1).

781320691 is an equidigital number, since it uses as much as digits as its factorization.

781320691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 37.

The square root of 781320691 is about 27952.1142491941. The cubic root of 781320691 is about 921.0356527952.

The spelling of 781320691 in words is "seven hundred eighty-one million, three hundred twenty thousand, six hundred ninety-one".