21665185091 has 16 divisors (see below), whose sum is σ = 24377809248. Its totient is φ = 19080979200.

The previous prime is 21665185079. The next prime is 21665185103. The reversal of 21665185091 is 19058156612.

It is an interprime number because it is at equal distance from previous prime (21665185079) and next prime (21665185103).

It is a cyclic number.

It is not a de Polignac number, because 21665185091 - 2²² = 21660990787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21665185291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19400 + ... + 209061.

It is an arithmetic number, because the mean of its divisors is an integer number (1523613078).

Almost surely, 2^21665185091 is an apocalyptic number.

21665185091 is a deficient number, since it is larger than the sum of its proper divisors (2712624157).

21665185091 is a wasteful number, since it uses less digits than its factorization.

21665185091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228742.

The product of its (nonzero) digits is 129600, while the sum is 44.

The spelling of 21665185091 in words is "twenty-one billion, six hundred sixty-five million, one hundred eighty-five thousand, ninety-one".