21021361 has 4 divisors (see below), whose sum is σ = 21468672. Its totient is φ = 20574052.

The previous prime is 21021359. The next prime is 21021383. The reversal of 21021361 is 16312012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21021361 - 2¹ = 21021359 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21021331) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 223585 + ... + 223678.

It is an arithmetic number, because the mean of its divisors is an integer number (5367168).

Almost surely, 2^21021361 is an apocalyptic number.

It is an amenable number.

21021361 is a deficient number, since it is larger than the sum of its proper divisors (447311).

21021361 is an equidigital number, since it uses as much as digits as its factorization.

21021361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 447310.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21021361 is about 4584.9057787483. The cubic root of 21021361 is about 275.9859309849.

Adding to 21021361 its reverse (16312012), we get a palindrome (37333373).

The spelling of 21021361 in words is "twenty-one million, twenty-one thousand, three hundred sixty-one".