21287960 has 16 divisors (see below), whose sum is σ = 47898000. Its totient is φ = 8515168.

The previous prime is 21287951. The next prime is 21287993. The reversal of 21287960 is 6978212.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21287960.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266060 + ... + 266139.

It is an arithmetic number, because the mean of its divisors is an integer number (2993625).

Almost surely, 2^21287960 is an apocalyptic number.

21287960 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21287960 is an abundant number, since it is smaller than the sum of its proper divisors (26610040).

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

21287960 is a wasteful number, since it uses less digits than its factorization.

21287960 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532210 (or 532206 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21287960 is about 4613.8877316207. The cubic root of 21287960 is about 277.1477444745.

The spelling of 21287960 in words is "twenty-one million, two hundred eighty-seven thousand, nine hundred sixty".