21164405 has 16 divisors (see below), whose sum is σ = 27551664. Its totient is φ = 15544320.

The previous prime is 21164401. The next prime is 21164431. The reversal of 21164405 is 50446112.

It can be written as a sum of positive squares in 8 ways, for example, as 22801 + 21141604 = 151^2 + 4598^2 .

It is not a de Polignac number, because 21164405 - 2² = 21164401 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164401) 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 15 ways as a sum of consecutive naturals, for example, 449 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (1721979).

Almost surely, 2^21164405 is an apocalyptic number.

It is an amenable number.

21164405 is a deficient number, since it is larger than the sum of its proper divisors (6387259).

21164405 is a wasteful number, since it uses less digits than its factorization.

21164405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6136.

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21164405 is about 4600.4787794315. The cubic root of 21164405 is about 276.6105166610.

The spelling of 21164405 in words is "twenty-one million, one hundred sixty-four thousand, four hundred five".