21280660 has 24 divisors (see below), whose sum is σ = 45642240. Its totient is φ = 8330784.

The previous prime is 21280639. The next prime is 21280687. The reversal of 21280660 is 6608212.

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, 10380 + ... + 12259.

It is an arithmetic number, because the mean of its divisors is an integer number (1901760).

Almost surely, 2^21280660 is an apocalyptic number.

21280660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21280660 is an abundant number, since it is smaller than the sum of its proper divisors (24361580).

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

21280660 is a wasteful number, since it uses less digits than its factorization.

21280660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22695 (or 22693 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21280660 is about 4613.0965738861. The cubic root of 21280660 is about 277.1160613096.

Adding to 21280660 its reverse (6608212), we get a palindrome (27888872).

The spelling of 21280660 in words is "twenty-one million, two hundred eighty thousand, six hundred sixty".