645738672 has 80 divisors (see below), whose sum is σ = 1704890880. Its totient is φ = 210560256.

The previous prime is 645738671. The next prime is 645738673. The reversal of 645738672 is 276837546.

It is an interprime number because it is at equal distance from previous prime (645738671) and next prime (645738673).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is not an unprimeable number, because it can be changed into a prime (645738671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 433513 + ... + 434999.

It is an arithmetic number, because the mean of its divisors is an integer number (21311136).

Almost surely, 2^645738672 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 645738672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (852445440).

645738672 is an abundant number, since it is smaller than the sum of its proper divisors (1059152208).

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

645738672 is a wasteful number, since it uses less digits than its factorization.

645738672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1690 (or 1684 counting only the distinct ones).

The product of its digits is 1693440, while the sum is 48.

The square root of 645738672 is about 25411.3886279361. The cubic root of 645738672 is about 864.3419642582.

The spelling of 645738672 in words is "six hundred forty-five million, seven hundred thirty-eight thousand, six hundred seventy-two".