1781091797 has 2 divisors, whose sum is σ = 1781091798. Its totient is φ = 1781091796.

The previous prime is 1781091761. The next prime is 1781091799. The reversal of 1781091797 is 7971901871.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1771904836 + 9186961 = 42094^2 + 3031^2 .

It is a cyclic number.

It is not a de Polignac number, because 1781091797 - 2¹⁸ = 1780829653 is a prime.

Together with 1781091799, 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 (1781091799) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 890545898 + 890545899.

It is an arithmetic number, because the mean of its divisors is an integer number (890545899).

Almost surely, 2^1781091797 is an apocalyptic number.

It is an amenable number.

1781091797 is a deficient number, since it is larger than the sum of its proper divisors (1).

1781091797 is an equidigital number, since it uses as much as digits as its factorization.

1781091797 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 222264, while the sum is 50.

The square root of 1781091797 is about 42202.9832713281. The cubic root of 1781091797 is about 1212.1660078697.

The spelling of 1781091797 in words is "one billion, seven hundred eighty-one million, ninety-one thousand, seven hundred ninety-seven".