21610109 has 4 divisors (see below), whose sum is σ = 22194204. Its totient is φ = 21026016.

The previous prime is 21610103. The next prime is 21610151. The reversal of 21610109 is 90101612.

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 20839225 + 770884 = 4565^2 + 878^2 .

It is a cyclic number.

It is not a de Polignac number, because 21610109 - 2⁴ = 21610093 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21610103) 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, 291992 + ... + 292065.

It is an arithmetic number, because the mean of its divisors is an integer number (5548551).

Almost surely, 2^21610109 is an apocalyptic number.

It is an amenable number.

21610109 is a deficient number, since it is larger than the sum of its proper divisors (584095).

21610109 is an equidigital number, since it uses as much as digits as its factorization.

21610109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 584094.

The product of its (nonzero) digits is 108, while the sum is 20.

The square root of 21610109 is about 4648.6674434724. The cubic root of 21610109 is about 278.5387693718.

The spelling of 21610109 in words is "twenty-one million, six hundred ten thousand, one hundred nine".