21020321 has 16 divisors (see below), whose sum is σ = 25277184. Its totient is φ = 17090304.

The previous prime is 21020303. The next prime is 21020339. The reversal of 21020321 is 12302012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21020303) and next prime (21020339).

It is not a de Polignac number, because 21020321 - 2¹⁴ = 21003937 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21020521) 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 15 ways as a sum of consecutive naturals, for example, 21581 + ... + 22533.

It is an arithmetic number, because the mean of its divisors is an integer number (1579824).

Almost surely, 2^21020321 is an apocalyptic number.

It is an amenable number.

21020321 is a deficient number, since it is larger than the sum of its proper divisors (4256863).

21020321 is a wasteful number, since it uses less digits than its factorization.

21020321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1120.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21020321 is about 4584.7923617106. The cubic root of 21020321 is about 275.9813795812.

Adding to 21020321 its reverse (12302012), we get a palindrome (33322333).

The spelling of 21020321 in words is "twenty-one million, twenty thousand, three hundred twenty-one".