21165161 has 4 divisors (see below), whose sum is σ = 21370752. Its totient is φ = 20959572.

The previous prime is 21165149. The next prime is 21165163. The reversal of 21165161 is 16156112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21165161 - 2⁶ = 21165097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21165163) 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, 102641 + ... + 102846.

It is an arithmetic number, because the mean of its divisors is an integer number (5342688).

Almost surely, 2^21165161 is an apocalyptic number.

It is an amenable number.

21165161 is a deficient number, since it is larger than the sum of its proper divisors (205591).

21165161 is a wasteful number, since it uses less digits than its factorization.

21165161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205590.

The product of its digits is 360, while the sum is 23.

The square root of 21165161 is about 4600.5609440589. The cubic root of 21165161 is about 276.6138101635.

The spelling of 21165161 in words is "twenty-one million, one hundred sixty-five thousand, one hundred sixty-one".