1644105820 has 72 divisors (see below), whose sum is σ = 4073055840. Its totient is φ = 555730560.

The previous prime is 1644105773. The next prime is 1644105823. The reversal of 1644105820 is 285014461.

It is a super-3 number, since 3×1644105820³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644105823) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 57766 + ... + 81394.

It is an arithmetic number, because the mean of its divisors is an integer number (56570220).

Almost surely, 2^1644105820 is an apocalyptic number.

1644105820 is a gapful number since it is divisible by the number (10) 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 1644105820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2036527920).

1644105820 is an abundant number, since it is smaller than the sum of its proper divisors (2428950020).

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

1644105820 is a wasteful number, since it uses less digits than its factorization.

1644105820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23723 (or 23714 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 1644105820 is about 40547.5747733450. The cubic root of 1644105820 is about 1180.2570109522.

The spelling of 1644105820 in words is "one billion, six hundred forty-four million, one hundred five thousand, eight hundred twenty".