21165280 has 24 divisors (see below), whose sum is σ = 50003352. Its totient is φ = 8466048.

The previous prime is 21165271. The next prime is 21165299. The reversal of 21165280 is 8256112.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65982 + ... + 66301.

It is an arithmetic number, because the mean of its divisors is an integer number (2083473).

Almost surely, 2^21165280 is an apocalyptic number.

21165280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21165280 is an abundant number, since it is smaller than the sum of its proper divisors (28838072).

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

21165280 is a wasteful number, since it uses less digits than its factorization.

21165280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132298 (or 132290 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21165280 is about 4600.5738772462. The cubic root of 21165280 is about 276.6143285780.

It can be divided in two parts, 2116 and 5280, that added together give a square (7396 = 86²).

The spelling of 21165280 in words is "twenty-one million, one hundred sixty-five thousand, two hundred eighty".