691637 has 2 divisors, whose sum is σ = 691638. Its totient is φ = 691636.

The previous prime is 691631. The next prime is 691651. The reversal of 691637 is 736196.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 538756 + 152881 = 734^2 + 391^2 .

It is a cyclic number.

It is not a de Polignac number, because 691637 - 2⁶ = 691573 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691637.

It is not a weakly prime, because it can be changed into another prime (691631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345818 + 345819.

It is an arithmetic number, because the mean of its divisors is an integer number (345819).

2⁶⁹¹⁶³⁷ is an apocalyptic number.

It is an amenable number.

691637 is a deficient number, since it is larger than the sum of its proper divisors (1).

691637 is an equidigital number, since it uses as much as digits as its factorization.

691637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 32.

The square root of 691637 is about 831.6471607599. The cubic root of 691637 is about 88.4353853956.

The spelling of 691637 in words is "six hundred ninety-one thousand, six hundred thirty-seven".