21917914209 has 27 divisors (see below), whose sum is σ = 32226556089. Its totient is φ = 14354637120.

The previous prime is 21917914199. The next prime is 21917914219. The reversal of 21917914209 is 90241971912.

It is a happy number.

The square root of 21917914209 is 148047.

It is a perfect power (a square), and thus also a powerful number.

21917914209 is a `hidden beast` number, since 219 + 1 + 7 + 9 + 1 + 420 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (21917914199) and next prime (21917914219).

It can be written as a sum of positive squares in 4 ways, for example, as 642774609 + 21275139600 = 25353^2 + 145860^2 .

It is not a de Polignac number, because 21917914209 - 2²¹ = 21915817057 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21917914219) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 27092197 + ... + 27093005.

Almost surely, 2^21917914209 is an apocalyptic number.

21917914209 is the 148047-th square number.

21917914209 is the 74024-th centered octagonal number.

It is an amenable number.

21917914209 is a deficient number, since it is larger than the sum of its proper divisors (10308641880).

21917914209 is an frugal number, since it uses more digits than its factorization.

21917914209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1746 (or 873 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The spelling of 21917914209 in words is "twenty-one billion, nine hundred seventeen million, nine hundred fourteen thousand, two hundred nine".