781997 has 2 divisors, whose sum is σ = 781998. Its totient is φ = 781996.

The previous prime is 781987. The next prime is 781999. The reversal of 781997 is 799187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 749956 + 32041 = 866^2 + 179^2 .

It is a cyclic number.

It is not a de Polignac number, because 781997 - 2⁸ = 781741 is a prime.

It is a super-2 number, since 2×781997² = 1223038616018, which contains 22 as substring.

Together with 781999, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390998 + 390999.

It is an arithmetic number, because the mean of its divisors is an integer number (390999).

2⁷⁸¹⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

781997 is a deficient number, since it is larger than the sum of its proper divisors (1).

781997 is an equidigital number, since it uses as much as digits as its factorization.

781997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31752, while the sum is 41.

The square root of 781997 is about 884.3059425335. The cubic root of 781997 is about 92.1301324781.

The spelling of 781997 in words is "seven hundred eighty-one thousand, nine hundred ninety-seven".