21165440 has 32 divisors (see below), whose sum is σ = 50600160. Its totient is φ = 8465920.

The previous prime is 21165427. The next prime is 21165457. The reversal of 21165440 is 4456112.

It is a tau number, because it is divible by the number of its divisors (32).

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, 15896 + ... + 17175.

It is an arithmetic number, because the mean of its divisors is an integer number (1581255).

Almost surely, 2^21165440 is an apocalyptic number.

21165440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21165440 is an abundant number, since it is smaller than the sum of its proper divisors (29434720).

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

21165440 is an equidigital number, since it uses as much as digits as its factorization.

21165440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33090 (or 33078 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21165440 is about 4600.5912663483. The cubic root of 21165440 is about 276.6150256029.

The spelling of 21165440 in words is "twenty-one million, one hundred sixty-five thousand, four hundred forty".