21650905 has 4 divisors (see below), whose sum is σ = 25981092. Its totient is φ = 17320720.

The previous prime is 21650903. The next prime is 21650917. The reversal of 21650905 is 50905612.

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 7354944 + 14295961 = 2712^2 + 3781^2 .

It is not a de Polignac number, because 21650905 - 2¹ = 21650903 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21650903) 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, 2165086 + ... + 2165095.

It is an arithmetic number, because the mean of its divisors is an integer number (6495273).

Almost surely, 2^21650905 is an apocalyptic number.

It is an amenable number.

21650905 is a deficient number, since it is larger than the sum of its proper divisors (4330187).

21650905 is an equidigital number, since it uses as much as digits as its factorization.

21650905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4330186.

The product of its (nonzero) digits is 2700, while the sum is 28.

The square root of 21650905 is about 4653.0532986417. The cubic root of 21650905 is about 278.7139362274.

The spelling of 21650905 in words is "twenty-one million, six hundred fifty thousand, nine hundred five".