21223705 has 8 divisors (see below), whose sum is σ = 25493832. Its totient is φ = 16962048.

The previous prime is 21223693. The next prime is 21223711. The reversal of 21223705 is 50732212.

It can be written as a sum of positive squares in 4 ways, for example, as 100489 + 21123216 = 317^2 + 4596^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21223705 - 2⁵ = 21223673 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6889 + ... + 9481.

It is an arithmetic number, because the mean of its divisors is an integer number (3186729).

Almost surely, 2^21223705 is an apocalyptic number.

It is an amenable number.

21223705 is a deficient number, since it is larger than the sum of its proper divisors (4270127).

21223705 is a wasteful number, since it uses less digits than its factorization.

21223705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4235.

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21223705 is about 4606.9192526025. The cubic root of 21223705 is about 276.8686183767.

Adding to 21223705 its reverse (50732212), we get a palindrome (71955917).

The spelling of 21223705 in words is "twenty-one million, two hundred twenty-three thousand, seven hundred five".