21768642 has 96 divisors (see below), whose sum is σ = 59371200. Its totient is φ = 5878656.

The previous prime is 21768641. The next prime is 21768667. The reversal of 21768642 is 24686712.

21768642 is a `hidden beast` number, since 2 + 1 + 7 + 6 + 8 + 642 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21768597 and 21768606.

It is not an unprimeable number, because it can be changed into a prime (21768641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 50058 + ... + 50490.

It is an arithmetic number, because the mean of its divisors is an integer number (618450).

Almost surely, 2^21768642 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21768642, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29685600).

21768642 is an abundant number, since it is smaller than the sum of its proper divisors (37602558).

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

21768642 is a wasteful number, since it uses less digits than its factorization.

21768642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 477 (or 464 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 21768642 is about 4665.6877306566. The cubic root of 21768642 is about 279.2182360018.

The spelling of 21768642 in words is "twenty-one million, seven hundred sixty-eight thousand, six hundred forty-two".