644240515840 has 36 divisors (see below), whose sum is σ = 1543157363664. Its totient is φ = 257696205824.

The previous prime is 644240515819. The next prime is 644240515859. The reversal of 644240515840 is 48515042446.

It is a happy number.

644240515840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 251655172 + ... + 251657731.

It is an arithmetic number, because the mean of its divisors is an integer number (42865482324).

Almost surely, 2^644240515840 is an apocalyptic number.

It is an amenable number.

644240515840 is an abundant number, since it is smaller than the sum of its proper divisors (898916847824).

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

644240515840 is an equidigital number, since it uses as much as digits as its factorization.

644240515840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503312924 (or 503312910 counting only the distinct ones).

The product of its (nonzero) digits is 614400, while the sum is 43.

The spelling of 644240515840 in words is "six hundred forty-four billion, two hundred forty million, five hundred fifteen thousand, eight hundred forty".