645646540 has 144 divisors (see below), whose sum is σ = 1740572064. Its totient is φ = 198912000.

The previous prime is 645646513. The next prime is 645646571. The reversal of 645646540 is 45646546.

It is a super-2 number, since 2×645646540² = 833718909227943200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 645646493 and 645646502.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1088484 + ... + 1089076.

It is an arithmetic number, because the mean of its divisors is an integer number (12087306).

Almost surely, 2^645646540 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 645646540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (870286032).

645646540 is an abundant number, since it is smaller than the sum of its proper divisors (1094925524).

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

645646540 is a wasteful number, since it uses less digits than its factorization.

645646540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 40.

The square root of 645646540 is about 25409.5757540341. The cubic root of 645646540 is about 864.3008550888.

The spelling of 645646540 in words is "six hundred forty-five million, six hundred forty-six thousand, five hundred forty".