644169240 has 512 divisors, whose sum is σ = 2607897600. Its totient is φ = 139345920.

The previous prime is 644169233. The next prime is 644169247. The reversal of 644169240 is 42961446.

644169240 is a `hidden beast` number, since 644 + 1 + 6 + 9 + 2 + 4 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (644169233) and next prime (644169247).

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

It is a junction number, because it is equal to n+sod(n) for n = 644169195 and 644169204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644169247) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 6640872 + ... + 6640968.

It is an arithmetic number, because the mean of its divisors is an integer number (5093550).

Almost surely, 2^644169240 is an apocalyptic number.

644169240 is a gapful number since it is divisible by the number (60) 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 644169240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1303948800).

644169240 is an abundant number, since it is smaller than the sum of its proper divisors (1963728360).

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

644169240 is a wasteful number, since it uses less digits than its factorization.

644169240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 174 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 644169240 is about 25380.4893569844. The cubic root of 644169240 is about 863.6411511327.

The spelling of 644169240 in words is "six hundred forty-four million, one hundred sixty-nine thousand, two hundred forty".