21121307 has 4 divisors (see below), whose sum is σ = 21170520. Its totient is φ = 21072096.

The previous prime is 21121277. The next prime is 21121319. The reversal of 21121307 is 70312112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21121307 - 2¹⁰ = 21120283 is a prime.

It is a super-2 number, since 2×21121307² = 892219218776498, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121207) 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, 23957 + ... + 24822.

It is an arithmetic number, because the mean of its divisors is an integer number (5292630).

Almost surely, 2^21121307 is an apocalyptic number.

21121307 is a deficient number, since it is larger than the sum of its proper divisors (49213).

21121307 is an equidigital number, since it uses as much as digits as its factorization.

21121307 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49212.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21121307 is about 4595.7923147157. The cubic root of 21121307 is about 276.4226310545.

Adding to 21121307 its reverse (70312112), we get a palindrome (91433419).

The spelling of 21121307 in words is "twenty-one million, one hundred twenty-one thousand, three hundred seven".