641808421 has 4 divisors (see below), whose sum is σ = 646493292. Its totient is φ = 637123552.

The previous prime is 641808379. The next prime is 641808451. The reversal of 641808421 is 124808146.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 124808146 = 2 ⋅62404073.

It can be written as a sum of positive squares in 2 ways, for example, as 291931396 + 349877025 = 17086^2 + 18705^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-641808421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641808451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2342230 + ... + 2342503.

It is an arithmetic number, because the mean of its divisors is an integer number (161623323).

Almost surely, 2^641808421 is an apocalyptic number.

It is an amenable number.

641808421 is a deficient number, since it is larger than the sum of its proper divisors (4684871).

641808421 is a wasteful number, since it uses less digits than its factorization.

641808421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4684870.

The product of its (nonzero) digits is 12288, while the sum is 34.

The square root of 641808421 is about 25333.9381265527. The cubic root of 641808421 is about 862.5848053838.

The spelling of 641808421 in words is "six hundred forty-one million, eight hundred eight thousand, four hundred twenty-one".