21122705 has 4 divisors (see below), whose sum is σ = 25347252. Its totient is φ = 16898160.

The previous prime is 21122677. The next prime is 21122707. The reversal of 21122705 is 50722112.

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 16265089 + 4857616 = 4033^2 + 2204^2 .

It is not a de Polignac number, because 21122705 - 2⁶ = 21122641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21122707) 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, 2112266 + ... + 2112275.

It is an arithmetic number, because the mean of its divisors is an integer number (6336813).

Almost surely, 2^21122705 is an apocalyptic number.

It is an amenable number.

21122705 is a deficient number, since it is larger than the sum of its proper divisors (4224547).

21122705 is an equidigital number, since it uses as much as digits as its factorization.

21122705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4224546.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21122705 is about 4595.9444078448. The cubic root of 21122705 is about 276.4287296404.

Adding to 21122705 its reverse (50722112), we get a palindrome (71844817).

The spelling of 21122705 in words is "twenty-one million, one hundred twenty-two thousand, seven hundred five".