641688491 has 2 divisors, whose sum is σ = 641688492. Its totient is φ = 641688490.

The previous prime is 641688479. The next prime is 641688497. The reversal of 641688491 is 194886146.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 641688491 - 2⁶ = 641688427 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (641688497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320844245 + 320844246.

It is an arithmetic number, because the mean of its divisors is an integer number (320844246).

Almost surely, 2^641688491 is an apocalyptic number.

641688491 is a deficient number, since it is larger than the sum of its proper divisors (1).

641688491 is an equidigital number, since it uses as much as digits as its factorization.

641688491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 331776, while the sum is 47.

The square root of 641688491 is about 25331.5710330015. The cubic root of 641688491 is about 862.5310737527.

The spelling of 641688491 in words is "six hundred forty-one million, six hundred eighty-eight thousand, four hundred ninety-one".