21018980 has 12 divisors (see below), whose sum is σ = 44139900. Its totient is φ = 8407584.

The previous prime is 21018979. The next prime is 21018989. The reversal of 21018980 is 8981012.

It can be written as a sum of positive squares in 2 ways, for example, as 16516096 + 4502884 = 4064^2 + 2122^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018989) 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, 525455 + ... + 525494.

It is an arithmetic number, because the mean of its divisors is an integer number (3678325).

Almost surely, 2^21018980 is an apocalyptic number.

21018980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21018980 is an abundant number, since it is smaller than the sum of its proper divisors (23120920).

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

21018980 is a wasteful number, since it uses less digits than its factorization.

21018980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050958 (or 1050956 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 21018980 is about 4584.6461150235. The cubic root of 21018980 is about 275.9755106746.

Adding to 21018980 its reverse (8981012), we get a palindrome (29999992).

The spelling of 21018980 in words is "twenty-one million, eighteen thousand, nine hundred eighty".