645861216 has 432 divisors, whose sum is σ = 2355236352. Its totient is φ = 151557120.

The previous prime is 645861193. The next prime is 645861217. The reversal of 645861216 is 612168546.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645861217) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 13741705 + ... + 13741751.

It is an arithmetic number, because the mean of its divisors is an integer number (5451936).

Almost surely, 2^645861216 is an apocalyptic number.

645861216 is a gapful number since it is divisible by the number (66) 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 645861216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1177618176).

645861216 is an abundant number, since it is smaller than the sum of its proper divisors (1709375136).

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

645861216 is a wasteful number, since it uses less digits than its factorization.

645861216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115 (or 83 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 645861216 is about 25413.7997159024. The cubic root of 645861216 is about 864.3966371606.

The spelling of 645861216 in words is "six hundred forty-five million, eight hundred sixty-one thousand, two hundred sixteen".