21680344 has 32 divisors (see below), whose sum is σ = 47412000. Its totient is φ = 9290400.

The previous prime is 21680341. The next prime is 21680353. The reversal of 21680344 is 44308612.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680341) 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 7 ways as a sum of consecutive naturals, for example, 1207 + ... + 6694.

It is an arithmetic number, because the mean of its divisors is an integer number (1481625).

Almost surely, 2^21680344 is an apocalyptic number.

It is an amenable number.

21680344 is an abundant number, since it is smaller than the sum of its proper divisors (25731656).

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

21680344 is an equidigital number, since it uses as much as digits as its factorization.

21680344 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7928 (or 7910 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 21680344 is about 4656.2156307456. The cubic root of 21680344 is about 278.8402025972.

Adding to 21680344 its reverse (44308612), we get a palindrome (65988956).

The spelling of 21680344 in words is "twenty-one million, six hundred eighty thousand, three hundred forty-four".