637691 has 2 divisors, whose sum is σ = 637692. Its totient is φ = 637690.

The previous prime is 637669. The next prime is 637699. The reversal of 637691 is 196736.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 637691 - 2⁶ = 637627 is a prime.

It is a super-2 number, since 2×637691² = 813299622962, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (637699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318845 + 318846.

It is an arithmetic number, because the mean of its divisors is an integer number (318846).

2⁶³⁷⁶⁹¹ is an apocalyptic number.

637691 is a deficient number, since it is larger than the sum of its proper divisors (1).

637691 is an equidigital number, since it uses as much as digits as its factorization.

637691 is an evil number, because the sum of its binary digits is even.

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

The square root of 637691 is about 798.5555710156. Note that the first 4 decimals coincide. The cubic root of 637691 is about 86.0736254308.

The spelling of 637691 in words is "six hundred thirty-seven thousand, six hundred ninety-one".