21765912 has 128 divisors (see below), whose sum is σ = 66908160. Its totient is φ = 5765760.

The previous prime is 21765901. The next prime is 21765917. The reversal of 21765912 is 21956712.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21765917) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 166087 + ... + 166217.

It is an arithmetic number, because the mean of its divisors is an integer number (522720).

Almost surely, 2^21765912 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21765912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33454080).

21765912 is an abundant number, since it is smaller than the sum of its proper divisors (45142248).

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

21765912 is a wasteful number, since it uses less digits than its factorization.

21765912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213 (or 209 counting only the distinct ones).

The product of its digits is 7560, while the sum is 33.

The square root of 21765912 is about 4665.3951601124. The cubic root of 21765912 is about 279.2065632839.

The spelling of 21765912 in words is "twenty-one million, seven hundred sixty-five thousand, nine hundred twelve".