21091110 has 32 divisors (see below), whose sum is σ = 51989472. Its totient is φ = 5472000.

The previous prime is 21091079. The next prime is 21091139. The reversal of 21091110 is 1119012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21091110.

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 15 ways as a sum of consecutive naturals, for example, 8391 + ... + 10610.

It is an arithmetic number, because the mean of its divisors is an integer number (1624671).

Almost surely, 2^21091110 is an apocalyptic number.

21091110 is an abundant number, since it is smaller than the sum of its proper divisors (30898362).

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

21091110 is a wasteful number, since it uses less digits than its factorization.

21091110 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19048.

The product of its (nonzero) digits is 18, while the sum is 15.

The square root of 21091110 is about 4592.5058519288. The cubic root of 21091110 is about 276.2908349919.

The spelling of 21091110 in words is "twenty-one million, ninety-one thousand, one hundred ten".