21162905 has 4 divisors (see below), whose sum is σ = 25395492. Its totient is φ = 16930320.

The previous prime is 21162893. The next prime is 21162907. The reversal of 21162905 is 50926112.

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 4946176 + 16216729 = 2224^2 + 4027^2 .

It is not a de Polignac number, because 21162905 - 2¹⁶ = 21097369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21162907) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2116286 + ... + 2116295.

It is an arithmetic number, because the mean of its divisors is an integer number (6348873).

Almost surely, 2^21162905 is an apocalyptic number.

It is an amenable number.

21162905 is a deficient number, since it is larger than the sum of its proper divisors (4232587).

21162905 is an equidigital number, since it uses as much as digits as its factorization.

21162905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4232586.

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

The square root of 21162905 is about 4600.3157500328. The cubic root of 21162905 is about 276.6039817017.

The spelling of 21162905 in words is "twenty-one million, one hundred sixty-two thousand, nine hundred five".