640722 has 8 divisors (see below), whose sum is σ = 1281456. Its totient is φ = 213572.

The previous prime is 640691. The next prime is 640727. The reversal of 640722 is 227046.

It is a happy number.

640722 is nontrivially palindromic in base 15.

640722 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.

640722 is an admirable number.

640722 is an undulating number in base 15.

It is not an unprimeable number, because it can be changed into a prime (640727) by changing a digit.

640722 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53388 + ... + 53399.

It is an arithmetic number, because the mean of its divisors is an integer number (160182).

2⁶⁴⁰⁷²² is an apocalyptic number.

640722 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640722 is a wasteful number, since it uses less digits than its factorization.

640722 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106792.

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 640722 is about 800.4511228051. The cubic root of 640722 is about 86.2097817113.

Adding to 640722 its reverse (227046), we get a palindrome (867768).

The spelling of 640722 in words is "six hundred forty thousand, seven hundred twenty-two".