645043440 has 80 divisors (see below), whose sum is σ = 2004478848. Its totient is φ = 171595008.

The previous prime is 645043429. The next prime is 645043457. The reversal of 645043440 is 44340546.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 645043398 and 645043407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 103287 + ... + 109353.

Almost surely, 2^645043440 is an apocalyptic number.

645043440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645043440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1002239424).

645043440 is an abundant number, since it is smaller than the sum of its proper divisors (1359435408).

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

645043440 is a wasteful number, since it uses less digits than its factorization.

645043440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6526 (or 6520 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 30.

The square root of 645043440 is about 25397.7054081663. The cubic root of 645043440 is about 864.0316560761.

Adding to 645043440 its reverse (44340546), we get a palindrome (689383986).

The spelling of 645043440 in words is "six hundred forty-five million, forty-three thousand, four hundred forty".