21001321 has 8 divisors (see below), whose sum is σ = 22968000. Its totient is φ = 19044240.

The previous prime is 21001319. The next prime is 21001349. The reversal of 21001321 is 12310012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001321 - 2¹ = 21001319 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001298 and 21001307.

It is not an unprimeable number, because it can be changed into a prime (21001381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2655 + ... + 7003.

It is an arithmetic number, because the mean of its divisors is an integer number (2871000).

Almost surely, 2^21001321 is an apocalyptic number.

It is an amenable number.

21001321 is a deficient number, since it is larger than the sum of its proper divisors (1966679).

21001321 is a wasteful number, since it uses less digits than its factorization.

21001321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4799.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21001321 is about 4582.7198256058. The cubic root of 21001321 is about 275.8982024991.

Adding to 21001321 its reverse (12310012), we get a palindrome (33311333).

The spelling of 21001321 in words is "twenty-one million, one thousand, three hundred twenty-one".