21020056 has 8 divisors (see below), whose sum is σ = 39412620. Its totient is φ = 10510024.

The previous prime is 21020053. The next prime is 21020057. The reversal of 21020056 is 65002012.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020053) 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 as a sum of consecutive naturals, namely, 1313746 + ... + 1313761.

Almost surely, 2^21020056 is an apocalyptic number.

It is an amenable number.

21020056 is a deficient number, since it is larger than the sum of its proper divisors (18392564).

21020056 is a wasteful number, since it uses less digits than its factorization.

21020056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2627513 (or 2627509 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21020056 is about 4584.7634617284. The cubic root of 21020056 is about 275.9802198245.

Adding to 21020056 its reverse (65002012), we get a palindrome (86022068).

The spelling of 21020056 in words is "twenty-one million, twenty thousand, fifty-six".