19821820 has 12 divisors (see below), whose sum is σ = 41625864. Its totient is φ = 7928720.

The previous prime is 19821799. The next prime is 19821829. The reversal of 19821820 is 2812891.

It is a happy number.

It is a super-2 number, since 2×19821820² = 785809096224800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19821829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 495526 + ... + 495565.

It is an arithmetic number, because the mean of its divisors is an integer number (3468822).

Almost surely, 2^19821820 is an apocalyptic number.

19821820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19821820 is an abundant number, since it is smaller than the sum of its proper divisors (21804044).

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

19821820 is a wasteful number, since it uses less digits than its factorization.

19821820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 991100 (or 991098 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 19821820 is about 4452.1702573015. The cubic root of 19821820 is about 270.6332643658.

The spelling of 19821820 in words is "nineteen million, eight hundred twenty-one thousand, eight hundred twenty".