20981800 has 72 divisors (see below), whose sum is σ = 56773710. Its totient is φ = 7190400.

The previous prime is 20981789. The next prime is 20981801. The reversal of 20981800 is 818902.

It can be written as a sum of positive squares in 3 ways, for example, as 19695844 + 1285956 = 4438^2 + 1134^2 .

It is a Harshad number since it is a multiple of its sum of digits (28).

It is not an unprimeable number, because it can be changed into a prime (20981801) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8730 + ... + 10870.

Almost surely, 2^20981800 is an apocalyptic number.

20981800 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 20981800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28386855).

20981800 is an abundant number, since it is smaller than the sum of its proper divisors (35791910).

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

20981800 is a wasteful number, since it uses less digits than its factorization.

20981800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2171 (or 2155 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 20981800 is about 4580.5894817152. The cubic root of 20981800 is about 275.8126923479.

The spelling of 20981800 in words is "twenty million, nine hundred eighty-one thousand, eight hundred".