21191718 has 16 divisors (see below), whose sum is σ = 42448896. Its totient is φ = 7053000.

The previous prime is 21191699. The next prime is 21191743. The reversal of 21191718 is 81719112.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 2155 + ... + 6857.

It is an arithmetic number, because the mean of its divisors is an integer number (2653056).

Almost surely, 2^21191718 is an apocalyptic number.

21191718 is an abundant number, since it is smaller than the sum of its proper divisors (21257178).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21191718 is a wasteful number, since it uses less digits than its factorization.

21191718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5459.

The product of its digits is 1008, while the sum is 30.

The square root of 21191718 is about 4603.4463177059. The cubic root of 21191718 is about 276.7294555964.

The spelling of 21191718 in words is "twenty-one million, one hundred ninety-one thousand, seven hundred eighteen".