644401261545156 has 36 divisors (see below), whose sum is σ = 1631534696537200. Its totient is φ = 214453408519728.

The previous prime is 644401261545133. The next prime is 644401261545157. The reversal of 644401261545156 is 651545162104446.

644401261545156 is a `hidden beast` number, since 6 + 4 + 4 + 4 + 0 + 1 + 2 + 615 + 4 + 5 + 15 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is not an unprimeable number, because it can be changed into a prime (644401261545157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14458810546 + ... + 14458855113.

Almost surely, 2^{644401261545156} is an apocalyptic number.

It is an amenable number.

644401261545156 is an abundant number, since it is smaller than the sum of its proper divisors (987133434992044).

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

644401261545156 is a wasteful number, since it uses less digits than its factorization.

644401261545156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28917666288 (or 28917666283 counting only the distinct ones).

The product of its (nonzero) digits is 13824000, while the sum is 54.

The spelling of 644401261545156 in words is "six hundred forty-four trillion, four hundred one billion, two hundred sixty-one million, five hundred forty-five thousand, one hundred fifty-six".