21198820 has 12 divisors (see below), whose sum is σ = 44517564. Its totient is φ = 8479520.

The previous prime is 21198809. The next prime is 21198829. The reversal of 21198820 is 2889112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5134756 + 16064064 = 2266^2 + 4008^2 .

It is not an unprimeable number, because it can be changed into a prime (21198829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 529951 + ... + 529990.

It is an arithmetic number, because the mean of its divisors is an integer number (3709797).

Almost surely, 2^21198820 is an apocalyptic number.

21198820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21198820 is an abundant number, since it is smaller than the sum of its proper divisors (23318744).

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

21198820 is a wasteful number, since it uses less digits than its factorization.

21198820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1059950 (or 1059948 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 21198820 is about 4604.2176316938. The cubic root of 21198820 is about 276.7603656762.

The spelling of 21198820 in words is "twenty-one million, one hundred ninety-eight thousand, eight hundred twenty".