21605182309 has 16 divisors (see below), whose sum is σ = 22943217600. Its totient is φ = 20274718464.

The previous prime is 21605182303. The next prime is 21605182369. The reversal of 21605182309 is 90328150612.

It is a cyclic number.

It is not a de Polignac number, because 21605182309 - 2¹⁵ = 21605149541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605182303) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12075787 + ... + 12077575.

It is an arithmetic number, because the mean of its divisors is an integer number (1433951100).

Almost surely, 2^21605182309 is an apocalyptic number.

It is an amenable number.

21605182309 is a deficient number, since it is larger than the sum of its proper divisors (1338035291).

21605182309 is a wasteful number, since it uses less digits than its factorization.

21605182309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3492.

The product of its (nonzero) digits is 25920, while the sum is 37.

The spelling of 21605182309 in words is "twenty-one billion, six hundred five million, one hundred eighty-two thousand, three hundred nine".