21200506165 has 16 divisors (see below), whose sum is σ = 25641615168. Its totient is φ = 16826766336.

The previous prime is 21200506133. The next prime is 21200506177. The reversal of 21200506165 is 56160500212.

It is a cyclic number.

It is not a de Polignac number, because 21200506165 - 2⁵ = 21200506133 is a prime.

It is a super-2 number, since 2×21200506165² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 447714 + ... + 492796.

It is an arithmetic number, because the mean of its divisors is an integer number (1602600948).

Almost surely, 2^21200506165 is an apocalyptic number.

It is an amenable number.

21200506165 is a deficient number, since it is larger than the sum of its proper divisors (4441109003).

21200506165 is a wasteful number, since it uses less digits than its factorization.

21200506165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45828.

The product of its (nonzero) digits is 3600, while the sum is 28.

The spelling of 21200506165 in words is "twenty-one billion, two hundred million, five hundred six thousand, one hundred sixty-five".