21020072 has 8 divisors (see below), whose sum is σ = 39412650. Its totient is φ = 10510032.

The previous prime is 21020059. The next prime is 21020081. The reversal of 21020072 is 27002012.

It can be written as a sum of positive squares in only one way, i.e., 20921476 + 98596 = 4574^2 + 314^2 .

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

It is an unprimeable number.

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, 1313747 + ... + 1313762.

Almost surely, 2^21020072 is an apocalyptic number.

It is an amenable number.

21020072 is a deficient number, since it is larger than the sum of its proper divisors (18392578).

21020072 is a wasteful number, since it uses less digits than its factorization.

21020072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2627515 (or 2627511 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 21020072 is about 4584.7652066382. The cubic root of 21020072 is about 275.9802898478.

Adding to 21020072 its reverse (27002012), we get a palindrome (48022084).

The spelling of 21020072 in words is "twenty-one million, twenty thousand, seventy-two".