634705781 has 2 divisors, whose sum is σ = 634705782. Its totient is φ = 634705780.

The previous prime is 634705739. The next prime is 634705817. The reversal of 634705781 is 187507436.

Together with next prime (634705817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 593360881 + 41344900 = 24359^2 + 6430^2 .

It is a cyclic number.

It is not a de Polignac number, because 634705781 - 2²² = 630511477 is a prime.

It is a super-2 number, since 2×634705781² = 805702856869639922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (634705381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 317352890 + 317352891.

It is an arithmetic number, because the mean of its divisors is an integer number (317352891).

Almost surely, 2^634705781 is an apocalyptic number.

It is an amenable number.

634705781 is a deficient number, since it is larger than the sum of its proper divisors (1).

634705781 is an equidigital number, since it uses as much as digits as its factorization.

634705781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 141120, while the sum is 41.

The square root of 634705781 is about 25193.3677978947. The cubic root of 634705781 is about 859.3910331968.

The spelling of 634705781 in words is "six hundred thirty-four million, seven hundred five thousand, seven hundred eighty-one".