491821820 has 72 divisors (see below), whose sum is σ = 1240283520. Its totient is φ = 163175040.

The previous prime is 491821801. The next prime is 491821853. The reversal of 491821820 is 28128194.

It is a super-2 number, since 2×491821820² = 483777405256224800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 22286 + ... + 38474.

It is an arithmetic number, because the mean of its divisors is an integer number (17226160).

Almost surely, 2^491821820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 491821820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (620141760).

491821820 is an abundant number, since it is smaller than the sum of its proper divisors (748461700).

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

491821820 is a wasteful number, since it uses less digits than its factorization.

491821820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16243 (or 16234 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 35.

The square root of 491821820 is about 22177.0561617181. The cubic root of 491821820 is about 789.3493654834.

The spelling of 491821820 in words is "four hundred ninety-one million, eight hundred twenty-one thousand, eight hundred twenty".