21090518 has 8 divisors (see below), whose sum is σ = 32490912. Its totient is φ = 10260216.

The previous prime is 21090497. The next prime is 21090529. The reversal of 21090518 is 81509012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

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 3 ways as a sum of consecutive naturals, for example, 142430 + ... + 142577.

It is an arithmetic number, because the mean of its divisors is an integer number (4061364).

Almost surely, 2^21090518 is an apocalyptic number.

21090518 is a deficient number, since it is larger than the sum of its proper divisors (11400394).

21090518 is a wasteful number, since it uses less digits than its factorization.

21090518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285046.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 21090518 is about 4592.4413986463. The cubic root of 21090518 is about 276.2882499264.

The spelling of 21090518 in words is "twenty-one million, ninety thousand, five hundred eighteen".