681991117 has 2 divisors, whose sum is σ = 681991118. Its totient is φ = 681991116.

The previous prime is 681991097. The next prime is 681991133. The reversal of 681991117 is 711199186.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 672572356 + 9418761 = 25934^2 + 3069^2 .

It is a cyclic number.

It is not a de Polignac number, because 681991117 - 2¹⁹ = 681466829 is a prime.

It is a super-2 number, since 2×681991117² = 930223767333815378, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681991517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340995558 + 340995559.

It is an arithmetic number, because the mean of its divisors is an integer number (340995559).

Almost surely, 2^681991117 is an apocalyptic number.

It is an amenable number.

681991117 is a deficient number, since it is larger than the sum of its proper divisors (1).

681991117 is an equidigital number, since it uses as much as digits as its factorization.

681991117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 43.

The square root of 681991117 is about 26114.9596400224. The cubic root of 681991117 is about 880.2233924078.

The spelling of 681991117 in words is "six hundred eighty-one million, nine hundred ninety-one thousand, one hundred seventeen".