21985311 has 4 divisors (see below), whose sum is σ = 29313752. Its totient is φ = 14656872.

The previous prime is 21985303. The next prime is 21985319. The reversal of 21985311 is 11358912.

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

It is an interprime number because it is at equal distance from previous prime (21985303) and next prime (21985319).

It is not a de Polignac number, because 21985311 - 2³ = 21985303 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 (21985319) 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, 3664216 + ... + 3664221.

It is an arithmetic number, because the mean of its divisors is an integer number (7328438).

Almost surely, 2^21985311 is an apocalyptic number.

21985311 is a deficient number, since it is larger than the sum of its proper divisors (7328441).

21985311 is an equidigital number, since it uses as much as digits as its factorization.

21985311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7328440.

The product of its digits is 2160, while the sum is 30.

The square root of 21985311 is about 4688.8496457020. The cubic root of 21985311 is about 280.1415568238.

The spelling of 21985311 in words is "twenty-one million, nine hundred eighty-five thousand, three hundred eleven".