21117907 has 4 divisors (see below), whose sum is σ = 21136320. Its totient is φ = 21099496.

The previous prime is 21117881. The next prime is 21117953. The reversal of 21117907 is 70971112.

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 21117907 - 2¹⁹ = 20593619 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21117997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7363 + ... + 9820.

It is an arithmetic number, because the mean of its divisors is an integer number (5284080).

Almost surely, 2^21117907 is an apocalyptic number.

21117907 is a deficient number, since it is larger than the sum of its proper divisors (18413).

21117907 is a wasteful number, since it uses less digits than its factorization.

21117907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18412.

The product of its (nonzero) digits is 882, while the sum is 28.

The square root of 21117907 is about 4595.4223962548. The cubic root of 21117907 is about 276.4077978913.

The spelling of 21117907 in words is "twenty-one million, one hundred seventeen thousand, nine hundred seven".