19921890 has 64 divisors (see below), whose sum is σ = 49766400. Its totient is φ = 5100480.

The previous prime is 19921877. The next prime is 19921901. The reversal of 19921890 is 9812991.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 100011 + ... + 100209.

It is an arithmetic number, because the mean of its divisors is an integer number (777600).

Almost surely, 2^19921890 is an apocalyptic number.

19921890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 19921890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24883200).

19921890 is an abundant number, since it is smaller than the sum of its proper divisors (29844510).

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

19921890 is a wasteful number, since it uses less digits than its factorization.

19921890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 19921890 is about 4463.3944481751. The cubic root of 19921890 is about 271.0879286940.

The spelling of 19921890 in words is "nineteen million, nine hundred twenty-one thousand, eight hundred ninety".