640992 has 48 divisors (see below), whose sum is σ = 1838592. Its totient is φ = 193920.

The previous prime is 640973. The next prime is 640993. The reversal of 640992 is 299046.

640992 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640992.

It is not an unprimeable number, because it can be changed into a prime (640993) by changing a digit.

640992 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 7 ways as a sum of consecutive naturals, for example, 753 + ... + 1359.

It is an arithmetic number, because the mean of its divisors is an integer number (38304).

2⁶⁴⁰⁹⁹² is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (919296).

640992 is an abundant number, since it is smaller than the sum of its proper divisors (1197600).

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

640992 is a wasteful number, since it uses less digits than its factorization.

640992 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 631 (or 623 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 640992 is about 800.6197599360. The cubic root of 640992 is about 86.2218896001.

The spelling of 640992 in words is "six hundred forty thousand, nine hundred ninety-two".