644219136 has 288 divisors, whose sum is σ = 2143747200. Its totient is φ = 189112320.

The previous prime is 644219119. The next prime is 644219141. The reversal of 644219136 is 631912446.

644219136 is a `hidden beast` number, since 644 + 2 + 1 + 9 + 1 + 3 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 644219136.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2813070 + ... + 2813298.

Almost surely, 2^644219136 is an apocalyptic number.

644219136 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644219136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1071873600).

644219136 is an abundant number, since it is smaller than the sum of its proper divisors (1499528064).

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

644219136 is a wasteful number, since it uses less digits than its factorization.

644219136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 302 (or 282 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 644219136 is about 25381.4722977214. The cubic root of 644219136 is about 863.6634491685.

The spelling of 644219136 in words is "six hundred forty-four million, two hundred nineteen thousand, one hundred thirty-six".