1821781836 has 144 divisors (see below), whose sum is σ = 5523202048. Its totient is φ = 495331200.

The previous prime is 1821781831. The next prime is 1821781837. The reversal of 1821781836 is 6381871281.

It is a happy number.

1821781836 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 1821781791 and 1821781800.

It is not an unprimeable number, because it can be changed into a prime (1821781831) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 474621 + ... + 478443.

Almost surely, 2^1821781836 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 1821781836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2761601024).

1821781836 is an abundant number, since it is smaller than the sum of its proper divisors (3701420212).

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

1821781836 is a wasteful number, since it uses less digits than its factorization.

1821781836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3932 (or 3927 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The square root of 1821781836 is about 42682.3363465497. The cubic root of 1821781836 is about 1221.3274621899.

The spelling of 1821781836 in words is "one billion, eight hundred twenty-one million, seven hundred eighty-one thousand, eight hundred thirty-six".