21680072 has 8 divisors (see below), whose sum is σ = 40650150. Its totient is φ = 10840032.

The previous prime is 21680069. The next prime is 21680077. The reversal of 21680072 is 27008612.

It can be written as a sum of positive squares in only one way, i.e., 21473956 + 206116 = 4634^2 + 454^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21680077) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1354997 + ... + 1355012.

Almost surely, 2^21680072 is an apocalyptic number.

It is an amenable number.

21680072 is a deficient number, since it is larger than the sum of its proper divisors (18970078).

21680072 is a wasteful number, since it uses less digits than its factorization.

21680072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2710015 (or 2710011 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21680072 is about 4656.1864223847. The cubic root of 21680072 is about 278.8390364895.

Adding to 21680072 its reverse (27008612), we get a palindrome (48688684).

The spelling of 21680072 in words is "twenty-one million, six hundred eighty thousand, seventy-two".