21680946 has 48 divisors (see below), whose sum is σ = 55683264. Its totient is φ = 6193584.

The previous prime is 21680921. The next prime is 21680947. The reversal of 21680946 is 64908612.

It is a self number, because there is not a number n which added to its sum of digits gives 21680946.

It is not an unprimeable number, because it can be changed into a prime (21680947) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 216 + ... + 6588.

It is an arithmetic number, because the mean of its divisors is an integer number (1160068).

Almost surely, 2^21680946 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21680946, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27841632).

21680946 is an abundant number, since it is smaller than the sum of its proper divisors (34002318).

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

21680946 is an equidigital number, since it uses as much as digits as its factorization.

21680946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6397 (or 6385 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 21680946 is about 4656.2802750694. The cubic root of 21680946 is about 278.8427834334.

The spelling of 21680946 in words is "twenty-one million, six hundred eighty thousand, nine hundred forty-six".