21111919 has 4 divisors (see below), whose sum is σ = 21125896. Its totient is φ = 21097944.

The previous prime is 21111877. The next prime is 21111931. The reversal of 21111919 is 91911112.

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 21111919 - 2⁷ = 21111791 is a prime.

It is a super-2 number, since 2×21111919² = 891426247725122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111893 and 21111902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21151919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4404 + ... + 7849.

It is an arithmetic number, because the mean of its divisors is an integer number (5281474).

Almost surely, 2^21111919 is an apocalyptic number.

21111919 is a deficient number, since it is larger than the sum of its proper divisors (13977).

21111919 is a wasteful number, since it uses less digits than its factorization.

21111919 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13976.

The product of its digits is 162, while the sum is 25.

The square root of 21111919 is about 4594.7708321526. The cubic root of 21111919 is about 276.3816702018.

The spelling of 21111919 in words is "twenty-one million, one hundred eleven thousand, nine hundred nineteen".