19890 has 48 divisors (see below), whose sum is σ = 58968. Its totient is φ = 4608.

The previous prime is 19889. The next prime is 19891. The reversal of 19890 is 9891.

19890 = 13² + 14² + ... + 39².

19890 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (19889) and next prime (19891).

It can be written as a sum of positive squares in 4 ways, for example, as 15129 + 4761 = 123^2 + 69^2 .

It is a super-2 number, since 2×19890² = 791224200, which contains 22 as substring.

19890 is an undulating number in base 13.

It is not an unprimeable number, because it can be changed into a prime (19891) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1162 + ... + 1178.

2¹⁹⁸⁹⁰ is an apocalyptic number.

19890 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 19890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29484).

19890 is an abundant number, since it is smaller than the sum of its proper divisors (39078).

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

19890 is a wasteful number, since it uses less digits than its factorization.

19890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43 (or 40 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 19890 is about 141.0319112825. The cubic root of 19890 is about 27.0943203286.

Subtracting from 19890 its reverse (9891), we obtain a palindrome (9999).

It can be divided in two parts, 19 and 890, that added together give a palindrome (909).

The spelling of 19890 in words is "nineteen thousand, eight hundred ninety".