21868311 has 4 divisors (see below), whose sum is σ = 29157752. Its totient is φ = 14578872.

The previous prime is 21868303. The next prime is 21868321. The reversal of 21868311 is 11386812.

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

It is not a de Polignac number, because 21868311 - 2³ = 21868303 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 (21868321) 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, 3644716 + ... + 3644721.

It is an arithmetic number, because the mean of its divisors is an integer number (7289438).

Almost surely, 2^21868311 is an apocalyptic number.

21868311 is a deficient number, since it is larger than the sum of its proper divisors (7289441).

21868311 is an equidigital number, since it uses as much as digits as its factorization.

21868311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7289440.

The product of its digits is 2304, while the sum is 30.

The square root of 21868311 is about 4676.3565946151. The cubic root of 21868311 is about 279.6437262892.

The spelling of 21868311 in words is "twenty-one million, eight hundred sixty-eight thousand, three hundred eleven".