21768336 has 30 divisors (see below), whose sum is σ = 60921510. Its totient is φ = 7256064.

The previous prime is 21768323. The next prime is 21768337. The reversal of 21768336 is 63386712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21678336 + 90000 = 4656^2 + 300^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21768336.

It is not an unprimeable number, because it can be changed into a prime (21768337) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75441 + ... + 75728.

It is an arithmetic number, because the mean of its divisors is an integer number (2030717).

Almost surely, 2^21768336 is an apocalyptic number.

It is an amenable number.

21768336 is an abundant number, since it is smaller than the sum of its proper divisors (39153174).

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

21768336 is a wasteful number, since it uses less digits than its factorization.

21768336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151183 (or 151174 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21768336 is about 4665.6549379482. The cubic root of 21768336 is about 279.2169276798.

The spelling of 21768336 in words is "twenty-one million, seven hundred sixty-eight thousand, three hundred thirty-six".