21989311 has 4 divisors (see below), whose sum is σ = 22945392. Its totient is φ = 21033232.

The previous prime is 21989291. The next prime is 21989369. The reversal of 21989311 is 11398912.

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 21989311 - 2⁷ = 21989183 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 (21989371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 478006 + ... + 478051.

It is an arithmetic number, because the mean of its divisors is an integer number (5736348).

Almost surely, 2^21989311 is an apocalyptic number.

21989311 is a deficient number, since it is larger than the sum of its proper divisors (956081).

21989311 is an equidigital number, since it uses as much as digits as its factorization.

21989311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 956080.

The product of its digits is 3888, while the sum is 34.

The square root of 21989311 is about 4689.2761701568. The cubic root of 21989311 is about 280.1585454134.

The spelling of 21989311 in words is "twenty-one million, nine hundred eighty-nine thousand, three hundred eleven".