21101321 has 4 divisors (see below), whose sum is σ = 21110544. Its totient is φ = 21092100.

The previous prime is 21101317. The next prime is 21101323. The reversal of 21101321 is 12310112.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21101321 - 2² = 21101317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21101323) 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, 1706 + ... + 6716.

It is an arithmetic number, because the mean of its divisors is an integer number (5277636).

Almost surely, 2^21101321 is an apocalyptic number.

It is an amenable number.

21101321 is a deficient number, since it is larger than the sum of its proper divisors (9223).

21101321 is an equidigital number, since it uses as much as digits as its factorization.

21101321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9222.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21101321 is about 4593.6174198555. The cubic root of 21101321 is about 276.3354153950.

Adding to 21101321 its reverse (12310112), we get a palindrome (33411433).

The spelling of 21101321 in words is "twenty-one million, one hundred one thousand, three hundred twenty-one".