645972 has 12 divisors (see below), whose sum is σ = 1507296. Its totient is φ = 215320.

The previous prime is 645941. The next prime is 645973. The reversal of 645972 is 279546.

It is a tau number, because it is divible by the number of its divisors (12).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645973) by changing a digit.

645972 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26904 + ... + 26927.

It is an arithmetic number, because the mean of its divisors is an integer number (125608).

2⁶⁴⁵⁹⁷² is an apocalyptic number.

It is an amenable number.

645972 is an abundant number, since it is smaller than the sum of its proper divisors (861324).

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

645972 is a wasteful number, since it uses less digits than its factorization.

645972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53838 (or 53836 counting only the distinct ones).

The product of its digits is 15120, while the sum is 33.

The square root of 645972 is about 803.7238331666. The cubic root of 645972 is about 86.4446057397. Note that the first 3 decimals are identical.

The spelling of 645972 in words is "six hundred forty-five thousand, nine hundred seventy-two".