21165001 has 16 divisors (see below), whose sum is σ = 25159680. Its totient is φ = 17550720.

The previous prime is 21164989. The next prime is 21165007. The reversal of 21165001 is 10056112.

It is a happy number.

It is not a de Polignac number, because 21165001 - 2⁹ = 21164489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21165007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11896 + ... + 13558.

It is an arithmetic number, because the mean of its divisors is an integer number (1572480).

Almost surely, 2^21165001 is an apocalyptic number.

It is an amenable number.

21165001 is a deficient number, since it is larger than the sum of its proper divisors (3994679).

21165001 is a wasteful number, since it uses less digits than its factorization.

21165001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1776.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 21165001 is about 4600.5435548422. The cubic root of 21165001 is about 276.6131131325.

Subtracting from 21165001 its reverse (10056112), we obtain a square (11108889 = 3333²).

It can be divided in two parts, 2116 and 5001, that added together give a palindrome (7117).

The spelling of 21165001 in words is "twenty-one million, one hundred sixty-five thousand, one".