21126905 has 4 divisors (see below), whose sum is σ = 25352292. Its totient is φ = 16901520.

The previous prime is 21126901. The next prime is 21126929. The reversal of 21126905 is 50962112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11806096 + 9320809 = 3436^2 + 3053^2 .

It is not a de Polignac number, because 21126905 - 2² = 21126901 is a prime.

It is a super-2 number, since 2×21126905² = 892692229758050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21126901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2112686 + ... + 2112695.

It is an arithmetic number, because the mean of its divisors is an integer number (6338073).

Almost surely, 2^21126905 is an apocalyptic number.

It is an amenable number.

21126905 is a deficient number, since it is larger than the sum of its proper divisors (4225387).

21126905 is an equidigital number, since it uses as much as digits as its factorization.

21126905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4225386.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21126905 is about 4596.4013097205. The cubic root of 21126905 is about 276.4470499537.

The spelling of 21126905 in words is "twenty-one million, one hundred twenty-six thousand, nine hundred five".