21161905 has 8 divisors (see below), whose sum is σ = 25752384. Its totient is φ = 16690800.

The previous prime is 21161887. The next prime is 21161911. The reversal of 21161905 is 50916112.

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

It is not a de Polignac number, because 21161905 - 2¹¹ = 21159857 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21161905.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29451 + ... + 30160.

It is an arithmetic number, because the mean of its divisors is an integer number (3219048).

Almost surely, 2^21161905 is an apocalyptic number.

It is an amenable number.

21161905 is a deficient number, since it is larger than the sum of its proper divisors (4590479).

21161905 is an equidigital number, since it uses as much as digits as its factorization.

21161905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59687.

The product of its (nonzero) digits is 540, while the sum is 25.

The square root of 21161905 is about 4600.2070605572. The cubic root of 21161905 is about 276.5996248906.

The spelling of 21161905 in words is "twenty-one million, one hundred sixty-one thousand, nine hundred five".