19991900 has 36 divisors (see below), whose sum is σ = 44788800. Its totient is φ = 7737600.

The previous prime is 19991893. The next prime is 19991911. The reversal of 19991900 is 919991.

It is a happy number.

It is a super-2 number, since 2×19991900² = 799352131220000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 125 + ... + 6324.

Almost surely, 2^19991900 is an apocalyptic number.

19991900 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19991900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22394400).

19991900 is an abundant number, since it is smaller than the sum of its proper divisors (24796900).

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

19991900 is a wasteful number, since it uses less digits than its factorization.

19991900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6494 (or 6487 counting only the distinct ones).

The product of its (nonzero) digits is 6561, while the sum is 38.

The square root of 19991900 is about 4471.2302557574. The cubic root of 19991900 is about 271.4051120735.

The spelling of 19991900 in words is "nineteen million, nine hundred ninety-one thousand, nine hundred".