1643440641 has 4 divisors (see below), whose sum is σ = 2191254192. Its totient is φ = 1095627092.

The previous prime is 1643440637. The next prime is 1643440657. The reversal of 1643440641 is 1460443461.

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 1643440641 - 2² = 1643440637 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1643440691) 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, 273906771 + ... + 273906776.

It is an arithmetic number, because the mean of its divisors is an integer number (547813548).

Almost surely, 2^1643440641 is an apocalyptic number.

It is an amenable number.

1643440641 is a deficient number, since it is larger than the sum of its proper divisors (547813551).

1643440641 is an equidigital number, since it uses as much as digits as its factorization.

1643440641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 547813550.

The product of its (nonzero) digits is 27648, while the sum is 33.

The square root of 1643440641 is about 40539.3714924146. The cubic root of 1643440641 is about 1180.0978184254.

It can be divided in two parts, 16434 and 40641, that added together give a palindrome (57075).

The spelling of 1643440641 in words is "one billion, six hundred forty-three million, four hundred forty thousand, six hundred forty-one".