1999209820 has 24 divisors (see below), whose sum is σ = 4277556864. Its totient is φ = 784595136.

The previous prime is 1999209803. The next prime is 1999209829. The reversal of 1999209820 is 289029991.

It is a happy number.

It is a hoax number, since the sum of its digits (49) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1999209829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 941964 + ... + 944083.

It is an arithmetic number, because the mean of its divisors is an integer number (178231536).

Almost surely, 2^1999209820 is an apocalyptic number.

1999209820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1999209820 is an abundant number, since it is smaller than the sum of its proper divisors (2278347044).

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

1999209820 is a wasteful number, since it uses less digits than its factorization.

1999209820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1886109 (or 1886107 counting only the distinct ones).

The product of its (nonzero) digits is 209952, while the sum is 49.

The square root of 1999209820 is about 44712.5241962473. The cubic root of 1999209820 is about 1259.7551006355.

The spelling of 1999209820 in words is "one billion, nine hundred ninety-nine million, two hundred nine thousand, eight hundred twenty".