643961941 has 4 divisors (see below), whose sum is σ = 735956512. Its totient is φ = 551967372.

The previous prime is 643961939. The next prime is 643961957. The reversal of 643961941 is 149169346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 643961941 - 2¹ = 643961939 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 (643961971) 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, 45997275 + ... + 45997288.

It is an arithmetic number, because the mean of its divisors is an integer number (183989128).

Almost surely, 2^643961941 is an apocalyptic number.

It is an amenable number.

643961941 is a deficient number, since it is larger than the sum of its proper divisors (91994571).

643961941 is an equidigital number, since it uses as much as digits as its factorization.

643961941 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91994570.

The product of its digits is 139968, while the sum is 43.

The square root of 643961941 is about 25376.4052024711. The cubic root of 643961941 is about 863.5484988999.

The spelling of 643961941 in words is "six hundred forty-three million, nine hundred sixty-one thousand, nine hundred forty-one".