641991609 has 16 divisors (see below), whose sum is σ = 1086970240. Its totient is φ = 366852240.

The previous prime is 641991607. The next prime is 641991611. The reversal of 641991609 is 906199146.

It is an interprime number because it is at equal distance from previous prime (641991607) and next prime (641991611).

It is not a de Polignac number, because 641991609 - 2¹ = 641991607 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (641991601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1698202 + ... + 1698579.

It is an arithmetic number, because the mean of its divisors is an integer number (67935640).

Almost surely, 2^641991609 is an apocalyptic number.

It is an amenable number.

641991609 is a deficient number, since it is larger than the sum of its proper divisors (444978631).

641991609 is a wasteful number, since it uses less digits than its factorization.

641991609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3396797 (or 3396791 counting only the distinct ones).

The product of its (nonzero) digits is 104976, while the sum is 45.

The square root of 641991609 is about 25337.5533349217. The cubic root of 641991609 is about 862.6668652575. Note that the first 3 decimals are identical.

The spelling of 641991609 in words is "six hundred forty-one million, nine hundred ninety-one thousand, six hundred nine".