21309121 has 8 divisors (see below), whose sum is σ = 22068224. Its totient is φ = 20554560.

The previous prime is 21309107. The next prime is 21309133. The reversal of 21309121 is 12190312.

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 21309121 - 2⁷ = 21308993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21309221) 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, 10441 + ... + 12313.

It is an arithmetic number, because the mean of its divisors is an integer number (2758528).

Almost surely, 2^21309121 is an apocalyptic number.

It is an amenable number.

21309121 is a deficient number, since it is larger than the sum of its proper divisors (759103).

21309121 is a wasteful number, since it uses less digits than its factorization.

21309121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2271.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21309121 is about 4616.1803474301. The cubic root of 21309121 is about 277.2395456811.

Adding to 21309121 its reverse (12190312), we get a palindrome (33499433).

The spelling of 21309121 in words is "twenty-one million, three hundred nine thousand, one hundred twenty-one".