21673505 has 16 divisors (see below), whose sum is σ = 30417024. Its totient is φ = 14515200.

The previous prime is 21673459. The next prime is 21673511. The reversal of 21673505 is 50537612.

It is not a de Polignac number, because 21673505 - 2¹⁰ = 21672481 is a prime.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian 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, 5696 + ... + 8705.

It is an arithmetic number, because the mean of its divisors is an integer number (1901064).

Almost surely, 2^21673505 is an apocalyptic number.

It is an amenable number.

21673505 is a deficient number, since it is larger than the sum of its proper divisors (8743519).

21673505 is a wasteful number, since it uses less digits than its factorization.

21673505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14456.

The product of its (nonzero) digits is 6300, while the sum is 29.

The square root of 21673505 is about 4655.4811781383. The cubic root of 21673505 is about 278.8108797430.

The spelling of 21673505 in words is "twenty-one million, six hundred seventy-three thousand, five hundred five".