21955609 has 4 divisors (see below), whose sum is σ = 23644516. Its totient is φ = 20266704.

The previous prime is 21955589. The next prime is 21955613. The reversal of 21955609 is 90655912.

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 11696400 + 10259209 = 3420^2 + 3203^2 .

It is a cyclic number.

It is not a de Polignac number, because 21955609 - 2¹³ = 21947417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21955649) 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, 844434 + ... + 844459.

It is an arithmetic number, because the mean of its divisors is an integer number (5911129).

Almost surely, 2^21955609 is an apocalyptic number.

It is an amenable number.

21955609 is a deficient number, since it is larger than the sum of its proper divisors (1688907).

21955609 is a wasteful number, since it uses less digits than its factorization.

21955609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1688906.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 21955609 is about 4685.6812738384. The cubic root of 21955609 is about 280.0153435469.

The spelling of 21955609 in words is "twenty-one million, nine hundred fifty-five thousand, six hundred nine".