21121309 has 16 divisors (see below), whose sum is σ = 24189120. Its totient is φ = 18264960.

The previous prime is 21121277. The next prime is 21121319. The reversal of 21121309 is 90312112.

It is a cyclic number.

It is not a de Polignac number, because 21121309 - 2⁵ = 21121277 is a prime.

It is a super-2 number, since 2×21121309² = 892219387746962, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121319) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22834 + ... + 23740.

It is an arithmetic number, because the mean of its divisors is an integer number (1511820).

Almost surely, 2^21121309 is an apocalyptic number.

21121309 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21121309 is a deficient number, since it is larger than the sum of its proper divisors (3067811).

21121309 is a wasteful number, since it uses less digits than its factorization.

21121309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1020.

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

The square root of 21121309 is about 4595.7925323060. The cubic root of 21121309 is about 276.4226397794.

The spelling of 21121309 in words is "twenty-one million, one hundred twenty-one thousand, three hundred nine".