641998691 has 4 divisors (see below), whose sum is σ = 648231792. Its totient is φ = 635765592.

The previous prime is 641998673. The next prime is 641998739. The reversal of 641998691 is 196899146.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 641998691 - 2²⁶ = 574889827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641998631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3116396 + ... + 3116601.

It is an arithmetic number, because the mean of its divisors is an integer number (162057948).

Almost surely, 2^641998691 is an apocalyptic number.

641998691 is a deficient number, since it is larger than the sum of its proper divisors (6233101).

641998691 is a wasteful number, since it uses less digits than its factorization.

641998691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6233100.

The product of its digits is 839808, while the sum is 53.

The square root of 641998691 is about 25337.6930875721. The cubic root of 641998691 is about 862.6700373573.

The spelling of 641998691 in words is "six hundred forty-one million, nine hundred ninety-eight thousand, six hundred ninety-one".