21218580 has 36 divisors (see below), whose sum is σ = 64363572. Its totient is φ = 5658240.

The previous prime is 21218551. The next prime is 21218599. The reversal of 21218580 is 8581212.

It can be written as a sum of positive squares in 2 ways, for example, as 14837904 + 6380676 = 3852^2 + 2526^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-3 number, since 3×21218580³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58761 + ... + 59120.

It is an arithmetic number, because the mean of its divisors is an integer number (1787877).

Almost surely, 2^21218580 is an apocalyptic number.

21218580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21218580 is an abundant number, since it is smaller than the sum of its proper divisors (43144992).

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

21218580 is a wasteful number, since it uses less digits than its factorization.

21218580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117896 (or 117891 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 21218580 is about 4606.3629904731. The cubic root of 21218580 is about 276.8463309407.

Adding to 21218580 its reverse (8581212), we get a palindrome (29799792).

It can be divided in two parts, 2121 and 8580, that added together give a palindrome (10701).

The spelling of 21218580 in words is "twenty-one million, two hundred eighteen thousand, five hundred eighty".