212021181820 has 24 divisors (see below), whose sum is σ = 508850836704. Its totient is φ = 72692976576.

The previous prime is 212021181809. The next prime is 212021181829. The reversal of 212021181820 is 28181120212.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (212021181829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 757218367 + ... + 757218646.

It is an arithmetic number, because the mean of its divisors is an integer number (21202118196).

Almost surely, 2^212021181820 is an apocalyptic number.

212021181820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

212021181820 is an abundant number, since it is smaller than the sum of its proper divisors (296829654884).

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

212021181820 is a wasteful number, since it uses less digits than its factorization.

212021181820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1514437029 (or 1514437027 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 28.

The spelling of 212021181820 in words is "two hundred twelve billion, twenty-one million, one hundred eighty-one thousand, eight hundred twenty".