644774487786 has 192 divisors, whose sum is σ = 1719155902464. Its totient is φ = 171854812800.

The previous prime is 644774487761. The next prime is 644774487787. The reversal of 644774487786 is 687784477446.

644774487786 is a `hidden beast` number, since 6 + 4 + 4 + 7 + 74 + 487 + 78 + 6 = 666.

It is not an unprimeable number, because it can be changed into a prime (644774487787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 15549421 + ... + 15590831.

It is an arithmetic number, because the mean of its divisors is an integer number (8953936992).

Almost surely, 2^644774487786 is an apocalyptic number.

644774487786 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 644774487786, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (859577951232).

644774487786 is an abundant number, since it is smaller than the sum of its proper divisors (1074381414678).

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

644774487786 is a wasteful number, since it uses less digits than its factorization.

644774487786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41729 (or 41726 counting only the distinct ones).

The product of its digits is 1416167424, while the sum is 72.

The spelling of 644774487786 in words is "six hundred forty-four billion, seven hundred seventy-four million, four hundred eighty-seven thousand, seven hundred eighty-six".