19891980 has 72 divisors (see below), whose sum is σ = 62589072. Its totient is φ = 5303232.

The previous prime is 19891973. The next prime is 19891981. The reversal of 19891980 is 8919891.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (19891981) 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, 2814 + ... + 6906.

Almost surely, 2^19891980 is an apocalyptic number.

19891980 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 19891980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31294536).

19891980 is an abundant number, since it is smaller than the sum of its proper divisors (42697092).

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

19891980 is a wasteful number, since it uses less digits than its factorization.

19891980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4117 (or 4103 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 45.

The square root of 19891980 is about 4460.0426006934. The cubic root of 19891980 is about 270.9521935614.

It can be divided in two parts, 1989 and 1980, that added together give a square (3969 = 63²).

The spelling of 19891980 in words is "nineteen million, eight hundred ninety-one thousand, nine hundred eighty".