21020680 has 16 divisors (see below), whose sum is σ = 47296620. Its totient is φ = 8408256.

The previous prime is 21020651. The next prime is 21020683. The reversal of 21020680 is 8602012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20016676 + 1004004 = 4474^2 + 1002^2 .

It is not an unprimeable number, because it can be changed into a prime (21020683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262719 + ... + 262798.

Almost surely, 2^21020680 is an apocalyptic number.

21020680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21020680 is an abundant number, since it is smaller than the sum of its proper divisors (26275940).

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

21020680 is a wasteful number, since it uses less digits than its factorization.

21020680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525528 (or 525524 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21020680 is about 4584.8315127167. The cubic root of 21020680 is about 275.9829507077.

Adding to 21020680 its reverse (8602012), we get a palindrome (29622692).

The spelling of 21020680 in words is "twenty-one million, twenty thousand, six hundred eighty".