781377991 has 2 divisors, whose sum is σ = 781377992. Its totient is φ = 781377990.

The previous prime is 781377929. The next prime is 781378009. The reversal of 781377991 is 199773187.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 781377991 - 2²⁹ = 244507079 is a prime.

It is a super-2 number, since 2×781377991² = 1221103129638392162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781377391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390688995 + 390688996.

It is an arithmetic number, because the mean of its divisors is an integer number (390688996).

Almost surely, 2^781377991 is an apocalyptic number.

781377991 is a deficient number, since it is larger than the sum of its proper divisors (1).

781377991 is an equidigital number, since it uses as much as digits as its factorization.

781377991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 666792, while the sum is 52.

The square root of 781377991 is about 27953.1391975928. The cubic root of 781377991 is about 921.0581676871.

The spelling of 781377991 in words is "seven hundred eighty-one million, three hundred seventy-seven thousand, nine hundred ninety-one".