21109247 has 4 divisors (see below), whose sum is σ = 22220280. Its totient is φ = 19998216.

The previous prime is 21109243. The next prime is 21109261. The reversal of 21109247 is 74290112.

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 21109247 - 2² = 21109243 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21109241) 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, 555488 + ... + 555525.

It is an arithmetic number, because the mean of its divisors is an integer number (5555070).

Almost surely, 2^21109247 is an apocalyptic number.

21109247 is a deficient number, since it is larger than the sum of its proper divisors (1111033).

21109247 is a wasteful number, since it uses less digits than its factorization.

21109247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1111032.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21109247 is about 4594.4800576344. The cubic root of 21109247 is about 276.3700097588.

Adding to 21109247 its reverse (74290112), we get a palindrome (95399359).

The spelling of 21109247 in words is "twenty-one million, one hundred nine thousand, two hundred forty-seven".