It is a congruent number.
It is an unprimeable number.
Almost surely, 2645739220 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 645739220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (825552000).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
645739220 is a wasteful number, since it uses less digits than its factorization.
645739220 is an evil number, because the sum of its binary digits is even.
The square root of 645739220 is about 25411.3994105008. The cubic root of 645739220 is about 864.3422087633.
The spelling of 645739220 in words is "six hundred forty-five million, seven hundred thirty-nine thousand, two hundred twenty".