20899980 has 72 divisors (see below), whose sum is σ = 64379952. Its totient is φ = 5486976.

The previous prime is 20899979. The next prime is 20899993. The reversal of 20899980 is 8999802.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11194 + ... + 12926.

It is an arithmetic number, because the mean of its divisors is an integer number (894166).

Almost surely, 2^20899980 is an apocalyptic number.

20899980 is a gapful number since it is divisible by the number (20) 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 20899980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32189976).

20899980 is an abundant number, since it is smaller than the sum of its proper divisors (43479972).

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

20899980 is a wasteful number, since it uses less digits than its factorization.

20899980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1815 (or 1810 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 45.

The square root of 20899980 is about 4571.6495928713. The cubic root of 20899980 is about 275.4537083386.

The spelling of 20899980 in words is "twenty million, eight hundred ninety-nine thousand, nine hundred eighty".