21002180 has 24 divisors (see below), whose sum is σ = 44499672. Its totient is φ = 8325632.

The previous prime is 21002129. The next prime is 21002203. The reversal of 21002180 is 8120012.

It can be written as a sum of positive squares in 4 ways, for example, as 1359556 + 19642624 = 1166^2 + 4432^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2387 + ... + 6906.

It is an arithmetic number, because the mean of its divisors is an integer number (1854153).

Almost surely, 2^21002180 is an apocalyptic number.

21002180 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21002180 is an abundant number, since it is smaller than the sum of its proper divisors (23497492).

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

21002180 is a wasteful number, since it uses less digits than its factorization.

21002180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9415 (or 9413 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 21002180 is about 4582.8135462835. The cubic root of 21002180 is about 275.9019640613.

Adding to 21002180 its reverse (8120012), we get a palindrome (29122192).

The spelling of 21002180 in words is "twenty-one million, two thousand, one hundred eighty".