21680442 has 72 divisors (see below), whose sum is σ = 55912896. Its totient is φ = 6051024.

The previous prime is 21680419. The next prime is 21680443. The reversal of 21680442 is 24408612.

21680442 is a `hidden beast` number, since 216 + 8 + 0 + 442 = 666.

It is not an unprimeable number, because it can be changed into a prime (21680443) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 41193 + ... + 41715.

It is an arithmetic number, because the mean of its divisors is an integer number (776568).

Almost surely, 2^21680442 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21680442, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27956448).

21680442 is an abundant number, since it is smaller than the sum of its proper divisors (34232454).

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

21680442 is a wasteful number, since it uses less digits than its factorization.

21680442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592 (or 582 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 21680442 is about 4656.2261543014. The cubic root of 21680442 is about 278.8406227366.

It can be divided in two parts, 21680 and 442, that added together give a palindrome (22122).

The spelling of 21680442 in words is "twenty-one million, six hundred eighty thousand, four hundred forty-two".