691645637 has 2 divisors, whose sum is σ = 691645638. Its totient is φ = 691645636.

The previous prime is 691645609. The next prime is 691645649. The reversal of 691645637 is 736546196.

691645637 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 395771236 + 295874401 = 19894^2 + 17201^2 .

It is a cyclic number.

It is not a de Polignac number, because 691645637 - 2¹⁶ = 691580101 is a prime.

It is a super-2 number, since 2×691645637² = 956747374362271538, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 691645591 and 691645600.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691645607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345822818 + 345822819.

It is an arithmetic number, because the mean of its divisors is an integer number (345822819).

Almost surely, 2^691645637 is an apocalyptic number.

It is an amenable number.

691645637 is a deficient number, since it is larger than the sum of its proper divisors (1).

691645637 is an equidigital number, since it uses as much as digits as its factorization.

691645637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 816480, while the sum is 47.

The square root of 691645637 is about 26299.1565834344. The cubic root of 691645637 is about 884.3575351419.

The spelling of 691645637 in words is "six hundred ninety-one million, six hundred forty-five thousand, six hundred thirty-seven".