21388317 has 4 divisors (see below), whose sum is σ = 28517760. Its totient is φ = 14258876.

The previous prime is 21388313. The next prime is 21388327. The reversal of 21388317 is 71388312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21388317 - 2² = 21388313 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388313) 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, 3564717 + ... + 3564722.

It is an arithmetic number, because the mean of its divisors is an integer number (7129440).

Almost surely, 2^21388317 is an apocalyptic number.

It is an amenable number.

21388317 is a deficient number, since it is larger than the sum of its proper divisors (7129443).

21388317 is an equidigital number, since it uses as much as digits as its factorization.

21388317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7129442.

The product of its digits is 8064, while the sum is 33.

The square root of 21388317 is about 4624.7504797556. The cubic root of 21388317 is about 277.5825774860.

The spelling of 21388317 in words is "twenty-one million, three hundred eighty-eight thousand, three hundred seventeen".