691944731 has 2 divisors, whose sum is σ = 691944732. Its totient is φ = 691944730.

The previous prime is 691944713. The next prime is 691944779. The reversal of 691944731 is 137449196.

Together with previous prime (691944713) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691944731 is a prime.

It is a super-2 number, since 2×691944731² = 957575021517324722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (691944131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345972365 + 345972366.

It is an arithmetic number, because the mean of its divisors is an integer number (345972366).

Almost surely, 2^691944731 is an apocalyptic number.

691944731 is a deficient number, since it is larger than the sum of its proper divisors (1).

691944731 is an equidigital number, since it uses as much as digits as its factorization.

691944731 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 44.

The square root of 691944731 is about 26304.8423488908. The cubic root of 691944731 is about 884.4849934337.

The spelling of 691944731 in words is "six hundred ninety-one million, nine hundred forty-four thousand, seven hundred thirty-one".