21740409 has 12 divisors (see below), whose sum is σ = 31682196. Its totient is φ = 14364672.

The previous prime is 21740387. The next prime is 21740417. The reversal of 21740409 is 90404712.

It is a happy number.

21740409 is a `hidden beast` number, since 217 + 40 + 409 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 837225 + 20903184 = 915^2 + 4572^2 .

It is not a de Polignac number, because 21740409 - 2⁷ = 21740281 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21740419) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9672 + ... + 11705.

It is an arithmetic number, because the mean of its divisors is an integer number (2640183).

Almost surely, 2^21740409 is an apocalyptic number.

It is an amenable number.

21740409 is a deficient number, since it is larger than the sum of its proper divisors (9941787).

21740409 is a wasteful number, since it uses less digits than its factorization.

21740409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21496 (or 21493 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21740409 is about 4662.6611500301. The cubic root of 21740409 is about 279.0974723982.

The spelling of 21740409 in words is "twenty-one million, seven hundred forty thousand, four hundred nine".