21218680 has 32 divisors (see below), whose sum is σ = 54563040. Its totient is φ = 7274880.

The previous prime is 21218657. The next prime is 21218693. The reversal of 21218680 is 8681212.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37611 + ... + 38170.

It is an arithmetic number, because the mean of its divisors is an integer number (1705095).

Almost surely, 2^21218680 is an apocalyptic number.

21218680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21218680 is an abundant number, since it is smaller than the sum of its proper divisors (33344360).

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

21218680 is a wasteful number, since it uses less digits than its factorization.

21218680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75799 (or 75795 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21218680 is about 4606.3738450108. The cubic root of 21218680 is about 276.8467658518.

Adding to 21218680 its reverse (8681212), we get a palindrome (29899892).

It can be divided in two parts, 2121 and 8680, that added together give a palindrome (10801).

The spelling of 21218680 in words is "twenty-one million, two hundred eighteen thousand, six hundred eighty".