645989400 has 288 divisors, whose sum is σ = 2502339840. Its totient is φ = 146292480.

The previous prime is 645989389. The next prime is 645989419. The reversal of 645989400 is 4989546.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 2104047 + ... + 2104353.

It is an arithmetic number, because the mean of its divisors is an integer number (8688680).

Almost surely, 2^645989400 is an apocalyptic number.

645989400 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 645989400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1251169920).

645989400 is an abundant number, since it is smaller than the sum of its proper divisors (1856350440).

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

645989400 is a wasteful number, since it uses less digits than its factorization.

645989400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503 (or 491 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 645989400 is about 25416.3215277113. The cubic root of 645989400 is about 864.4538189443.

It can be divided in two parts, 6459 and 89400, that added together give a palindrome (95859).

The spelling of 645989400 in words is "six hundred forty-five million, nine hundred eighty-nine thousand, four hundred".