640721343 has 8 divisors (see below), whose sum is σ = 872471808. Its totient is φ = 418059224.

The previous prime is 640721321. The next prime is 640721359. The reversal of 640721343 is 343127046.

640721343 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640721343 - 2¹⁰ = 640720319 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640721343.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640721383) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2271921 + ... + 2272202.

It is an arithmetic number, because the mean of its divisors is an integer number (109058976).

Almost surely, 2^640721343 is an apocalyptic number.

640721343 is a deficient number, since it is larger than the sum of its proper divisors (231750465).

640721343 is a wasteful number, since it uses less digits than its factorization.

640721343 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4544173.

The product of its (nonzero) digits is 12096, while the sum is 30.

The square root of 640721343 is about 25312.4740592460. The cubic root of 640721343 is about 862.0975224458.

Adding to 640721343 its reverse (343127046), we get a palindrome (983848389).

The spelling of 640721343 in words is "six hundred forty million, seven hundred twenty-one thousand, three hundred forty-three".