19991020 has 36 divisors (see below), whose sum is σ = 48837600. Its totient is φ = 6853728.

The previous prime is 19991011. The next prime is 19991039. The reversal of 19991020 is 2019991.

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, 9220 + ... + 11179.

It is an arithmetic number, because the mean of its divisors is an integer number (1356600).

Almost surely, 2^19991020 is an apocalyptic number.

19991020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19991020 is an abundant number, since it is smaller than the sum of its proper divisors (28846580).

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

19991020 is a wasteful number, since it uses less digits than its factorization.

19991020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20422 (or 20413 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 19991020 is about 4471.1318477540. The cubic root of 19991020 is about 271.4011297940.

It can be divided in two parts, 199 and 91020, that added together give a palindrome (91219).

The spelling of 19991020 in words is "nineteen million, nine hundred ninety-one thousand, twenty".