644531218554 has 16 divisors (see below), whose sum is σ = 1316489298048. Its totient is φ = 210272596032.

The previous prime is 644531218553. The next prime is 644531218567. The reversal of 644531218554 is 455812135446.

It is a super-2 number, since 2×644531218554² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644531218553) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1142785567 + ... + 1142786130.

It is an arithmetic number, because the mean of its divisors is an integer number (82280581128).

Almost surely, 2^644531218554 is an apocalyptic number.

644531218554 is an abundant number, since it is smaller than the sum of its proper divisors (671958079494).

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

644531218554 is a wasteful number, since it uses less digits than its factorization.

644531218554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2285571749.

The product of its digits is 2304000, while the sum is 48.

The spelling of 644531218554 in words is "six hundred forty-four billion, five hundred thirty-one million, two hundred eighteen thousand, five hundred fifty-four".